The giants of the Web went on a buying binge last week, shopping for start-ups like it was 1999.

Google snapped up digital photo software maker Picasa; Yahoo acquired Web-mail vendor Oddpost; and Microsoft Corp. grabbed Lookout Software.

These companies didn't reveal the details of these acquisitions, but the spree has all the signs of a new arms race between major Web destinations eager to find better ways to woo and keep users.

Microsoft's purchase of Lookout (www.lookoutsoft.com) was perhaps the most puzzling. Wouldn't the world's largest software developer already have created tools to help users find data in its own e-mail program, Outlook? That's essentially what Lookout does, allowing users to search through their Outlook messages as well as other files on their computer.

Microsoft's stated explanation: The company will integrate Lookout's searching tools into the MSN Web search service.

Google, meanwhile, wouldn't say anything about its plans for Picasa (www.picasa.com). But it seems obvious that the Web search leader is remaking itself into a clone of Yahoo and MSN that will offer all sorts of services besides search. Picasa makes software to help people manage and share digital photos; Google already had a deal with it that let Picasa users add photos to Web journals hosted on Google's Blogger service.

Yahoo's purchase was less surprising. Oddpost's $30-a-year Web-mail service (www.oddpost.com) works quickly and offers mail-management features normally restricted to desktop e-mail programs. So how long will it take for Yahoo's Web-mail users to start seeing some of Oddpost's features?

EBay Explores Music

Until now, you could buy music on eBay on everything from CD to 8-track tape, but not as digital downloads. That's changing: Ebay spokesman Hani Durzy said the online auctioneer has preapproved a "very small" number of companies (including one record label) to sell licensed digital-music downloads during a 180-day test that kicks off this week. Previously, eBay banned the sale of digital music.

music.ebay.com

Amazon Plugs Away With 'Plogs'

Amazon.com is trying to capitalize on the popularity of blogs by naming its latest feature "plogs," short for a personalized blog. But unlike a blog -- a personal diary written by one person for many to read -- Amazon's plogs are shopping diaries automatically prepared for individual users.

Plogs, still in test form, replace the first page some shoppers see on the site. They debuted in early June, went dormant and now are online again, said Amazon's Craig Berman.

www.amazon.com

E-mail Leslie Walker at walkerl@washpost.com.