To get the most out of your Treo 600, these additional software packages are necessary.
Adobe Acrobat Reader for Palm OS : Enables your device to view PDF files. The package also has a program that allows you to print from several programs to a fax machine, among other things.
pTunes or Pocket Tunes: Plays MP3 files from SD Cards. You can install various skins to change its look too.
QuickOffice : Open, view and edit Word, PowerPoint and Excel native formats.
Snappermail : POP3 email software that handles file attachments. This software package also includes a program for handling and creating ZIP files.
TreoSMS600 : For SprintPCS Treo 600 only, this allows full SMS functionality. Why does Sprint not allow this without third party software right now? I dunno. But given the fact that SprintPCS's CDMA network has twice the speed of GSM networks of the other carriers, I don't mind too much.
VeriChat : Enables you to chat on AOL, Yahoo, MSN and ICQ instant messaging all at once. It also allows you to keep these IM sessions open on standby 24/7.
Update on another cool program:
Skinner 2.0: Let's you change your dialpad and favorites screens with different skins.