You've seen them, and maybe you have one of your own. Personal digital assistants, or PDAs, are those little handheld computers that allow you to keep a calendar, an address book, and sometimes surf the Web and write email. They are very popular products these days. -- and since typically those who use them are Internet savvy, PDAs are popular to buy online.

We get a number of searches for PDAs, both by brand name and by model name, and we get searches for PDA software as well. Lately, we've noticed searches rising quickly for one PDA model in particular: the Handspring Treo.

The Treo looks different than most other Palm-style PDAs. It has a flip-up top, and a tiny keyboard at the bottom so that users don't need to memorize the special script used with Palm PDAs. Treo's added features go even further, however; with the exception of the new lower-cost Treo 90, the Treo models all cross a PDA with a cell phone and wireless email.

PDAs come in two main types, depending on what operating systems they use. The first set uses the Palm OS, the same format as the world-famous Palm Pilots. The Handspring Visor and Treo products are in this category, as is the Sony Clie. The other type of PDA uses Microsoft's format called Pocket PC. Compaq (the IPAQ), Hewlett-Packard (the Jornada), and Toshiba are among the companies that use this operating system.

When it comes to software searches online, its clear that Palm OS still runs circles around Pocket PC, and Palm's products are still the most popular PDA models. Treo's stock is rising,, but it still isn't close to the most popular Palm models, the Palm m515 and Palm m505, when it comes to Lycos queries. The most popular Pocket PC model, by the way, is the Compaq IPAQ 3670.

Lycos Shop has deals on all these products. Click here to check out the Handspring Treo, click here for the Palm m series, and click here for Lycos Shop's list of all PDAs.

TOMORROW: The Stone Cold Lycos 50.