The summer's stock market boom made money mostly for Wall Street professionals, but the record trading activity is begining to make the market more attractive to small investors.

For the first time in several years, many analysts are restoring stocks to the growing list of investment opportunities, and suggesting small investors shift their funds from the booming money funds to equity markets.

Personal financial planning has become more complex in recent years as interest rates have become crucial to individual investors' plans. The prime rate, Treasury bill rates and Donoghue's Money Fund Averages now rank alongside the Dow Jones stock averages as closely watched financial barometers.

The question facing investors today is whether a predicted rebound in interest rates will occur -- and if so, when. Higher rates not only would dampen the recovery and curtail the stock market's boom, but also make interest investments more attractive than stocks.

Interest rates have dropped substantially this year. As the Dow Jones Industrial Average enjoyed its meteoric three-week rise of 148 points in August, Donoghue's index of money market fund rates declined by 30 percent.

But no one can predict whether the decline of the past few months will continue or be reversed, and this doubt breeds uncertainty among investors trying to decide whether to make major long term strategic commitments or to capitalize on short-term market changes..

The conventional wisdom had been that as soon as interest rates go down, money market funds will be drained of dollars, which then will head for the stock market. But no wholesale move out of the funds into stocks has occurred yet.

Some investors are trying to take advantage of the lag factor which makes money fund averages go down more slowly than Treasury rates. Others want to avoid switching to new investments because they believe interest rates soon will start back up. Increasing numbers of Americans are using money market funds, which earn a current average return of 9.86 percent, as regular savings accounts.

"People are unlikely to go back to the 5 1/4 percent passbook accounts although they might investigate higher yields through certificates at savings banks," said William LeFevre, vice president-investment strategy, at New York's Purcell, Graham & Co. Inc.

Though bullish on the stock market, LeFevre said he recognizes that many investors are looking for comfortable returns and security. These days few investments offer more certainty than government and other types of high quality bonds.

But for investors less interested in long-term, fixed return instruments, LeFevre touts stocks. "Even though the market is up 150 points, there still are some outstanding values for those who want yield and a possible shot at a capital gain," he said.

Like many market professionals, LeFevre stresses quality, particularly large companies like oil concerns, such as Exxon, which pay dividends in excess of 10 percent of their stock price. In addition, he also is high on stocks in cyclical industries such as steel, paper and chemicals, and diversified retailers such as Sears, Roebuck & Co.

"You buy steel stocks when the smokestacks are cold and sell them when they're hot," he said, quoting a Wall Street cliche, which he said has relevance now with the economy potentially poised for at least a modest recovery.

On the other hand, LeFevre, like many stock experts, still is worried that interest rates might rise again, particularly after the fall congressional elections.

"Don't look for much from stocks unless interest rates continue to moderate," he warned. "One never knows what the Fed's stance will be after the election. It is well known that not only the Supreme Court but the Fed reads the election results."

But for the investor who believes interest rates will remain where they are now, good yields are available elsewhere. One of the most popular products is the tax-exempt unit investment trust, according to John Nuveen & Co., municipal bond specialists. In the first eight months of this year, investments in unit trusts totaled $7.8 billion, more than double that of last year.

The portfolio in these instruments remains the same for the 30-year length of the trust, so the yield -- currently 11.25 percent -- is assured. Investments can be redeemed before maturity at market value. If interest rates continue to drop, the value of the bonds in the trust increases and so does the value of the unit. If rates go up, the value goes down.

Starting next July, a 10 percent withholding tax will be imposed on interest and dividends. Because the individual does not have the use of that portion of his or her money, the effective yield on taxable investments is diminished by 98.7 cents per $1,000 invested. For large investors, this could increase slightly the attractiveness of tax-exempt investments. Tax-exempt money market funds currently pay about 6.65 percent, an effective yield of 13.30 percent to someone in the 50 percent tax bracket.

Public utility bonds still yield in excess of 14 percent. Long-term Treasury securities which are subject to federal but not state tax, now are paying between 11.25 and 12.65 percent.

There are an increasing array of opportunities in tax-free Treasury-backed bonds. Philadelphia's Butcher & Singer Inc. is aggressively marketing tax exempt "super bonds." The principal and interest on these bonds are paid from investments in Treasury securities in the hands of a bank trustee. They carry triple A ratings, provide a range of maturity options and recently have offered yields as high as 12 percent.

In addition, there are wide varieties of new zero coupon bonds, which pay no interest but are sold at a big discount from face value and increase in value until maturity.

Salomon Brothers Inc. now is marketing to individual investors through banks or brokerage houses, Certificates of Accrual on Treasury Securities (CATS). Merrill Lynch has its similar Treasury Investment Growth Receipts (TIGRs).

Salomon Brothers' CATS, primarily designed for use as Individual Retirement Accounts (IRAs) require a minimum investment of only $1,000. With CATS (or TIGRs), investors can double their money over six years or see it grow 10 fold over a 30-year span, said Robert W. Scully, a Salomon vice president. Unless the investment is made in the form of an IRA, or other tax free vehicle, investors in CATS are forced to pay yearly income taxes on the interest even though they do not collect it.

Other new vehicles are being developed in response to the expiration next month of some $32 billion in All Savers' certificates paying in excess of 12 percent tax free. The issuing banks and savings institutions, facing a potentially huge withdrawal, are beginning to offer incentives to savers to roll over their accounts. One Washington-area S&L offers an effective yield of 14 percent (taxable) for 3 1/2 years.

The regulatory ceiling now has been lifted from all certificates of deposit (CD) with maturities of 3 1/2 years or more, so savers may be able to benefit from competing offers. James Christian, chief economist of the U.S. League of Savings Associations, said he does not anticipate any upward surge in rates before next spring. "So if you are prepared to go long and somebody offers you a good deal, take it," he said.

Another way of picking up high yielding certificates of deposit is in the secondary CD market newly created by big brokerage houses. They now buy CDs before they mature and resell them at a small premium. With luck an investor might latch onto a 17 percent CD that has three years to run. For those who prefer short term investments, many banks and thrift institutions are offering retail repurchase agreements -- or in Maryland, insured variable rate accounts -- which now are paying about 10.65 percent.

Finally, for those who believe the economy really is on the way up, certified financial planner Alexandra Armstrong of Julia M. Walsh & Sons recommends, in addition to stocks, real estate partnerships and oil and gas income funds. The first benefits from battered property prices and favorable financing, while the second takes advantge of currently depressed resource prices and the prospect of future increases through natural gas deregulation, she noted.