After writing yesterday about the growing popularity of online "mashups," I couldn't help being slightly amused by today's announcement that Yahoo! (NASDAQ:YHOO) is jumping on the bandwagon, planning to release four tools that will help Web users mix and match their favorite online services.

According to CNET (NASDAQ:CNET), Yahoo! plans to release four developer tools to let folks build customized programs that use the search portal's many tools, including its photo, calendar, shopping, and bookmark services.

What's a mashup, you ask? It's a way for developers to create programs that integrate a bunch of their favorite services from around the Web -- flagging the locations of local Craigslist apartment listings on a Yahoo! map, for instance. The latest mashup tools are reaching out to people who have little or no programming experience. Just yesterday, Time Warner's (NYSE:TWX) America Online announced that it would open up its Instant Messenger service for use in mashups and other user-made modifications. I'm not hip enough to be playing around with mashups myself, but the practice seems to be gaining momentum. Plans like Yahoo!'s and AOL's will likely increase their sites' traffic, as the public finds new ways to make these services more useful and relevant than ever.

Granted, Yahoo! has lots to prove these days, especially after recent indications that it's backing off original content (although Yahoo!'s embrace of mashups proves that it will still use some user-generated content). Original Yahoo! video series never really resonated with me; I've been more interested by many of the company's recent acquisitions relating to social and collaborative online services. (Here's a delicious development, and an upcoming idea.) Embracing mashup culture is yet another way for Yahoo! to capitalize on the Web's increasing customization and creativity. If the phenomenon continues to flourish, don't be surprised to see strange bedfellows -- for example, a mashup combining data from two competing websites, complementing one another's strengths.

It's easy to get cynical when companies jump aboard the latest hot trends. However, given Yahoo!'s online prominence and string of recent acquisitions, I think its mashup plans are part of a savvy long-term strategy. As the Internet increasingly thrives on openness and imaginative applications, it bodes well for giants like Yahoo! to encourage their users' contributions.

Time Warner is a longtime Motley Fool Stock Advisor selection, while CNET is a Motley Fool Rule Breakers pick. Whatever your investing style, the Fool's got a newsletter to help you pursue it. See for yourself with a free 30-day guest pass.

Alyce Lomax does not own shares of any of the companies mentioned.