You did not mention specifications about memory,screen type,OS which you need.I will give details of few models of pdas and later you can choose the best you need.
Palm VIIx Handheld features an iMessenger and integrated wireless Internet access. The Date Book, Address Book, To-Do list and Memo pad are included in Palm VIIx Handheld. It has Backlit supported
Razor Sharp Screen Display and base memory of 8 MB.It costs about $449.
Jornada 680 has built in 56 kbps modem which allows you to stay in touch via e-mail and surf the Web.It has 65,536 color CSTN screen and base memory of 16 MB.
NB-80c GeoBook is provided with an internal 33.6/14.4 Kbps data/fax modem, e-mail software and the GlobeHopper Graphic Web Browser for accessing the internet. The GeoBook boots up with GEOS 3.0 operating system.It is featured with software suite of Internet and productivity applications including a web browser, e-mail, scheduler, desktop publisher, word processor, and spreadsheet.
Fex21 from Itronix is LAN compatible with both WAP phone and Internet capabilities. It supports Integrated Wireline Communications using 33.6 kbps V34bis PSTN soft modem via RJ11 connector. It runs on the Windows CE Handheld PC Professional Edition, V3.01 operating system.It has Backlit supported 1/2 VGA LCD color transflective/Monochrome screen.These are only few models of Pdas and if you want to know to know about some other models I suggest you to browse
www.solveit.com where you can find many more models and select the one you need.