DateBk5: My Handspring Visor had a program called Date Book+, an enhanced version of the standard Date Book. The Sony didn't have it, so I purchased DateBk5, which has all the features of Date Book+ and more.
powerOne Personal: The Visor also had an Advanced Calculator program which I liked. In addition to the usual calculator functions, it could do conversions. The Sony has the standard Calc program, and includes a calculator called powerOne Personal. I upgraded to the current version of this program to get access to a number of templates for conversions and other calculations.
Shadow Plan: Outliner. I use this a lot. I have a fascination with outliners, and have used a number of them over the years. The outline structure just seems a logical way to organize information.
pedit: Text editor; a powerful Memo Pad replacement. I don't use it much.
SplashID: Encrypted database for passwords, account numbers and other confidential information. Includes a desktop component so you can view/update the database in Windows.
SplashMoney: Financial management program. I use it as a cheque register.
BigClock: Shown in the photo. Displays the time in a large, easily readable font. Also has alarms, timers, etc.
Weasel Reader: For reading ebooks in DOC format. Also supports the zTXT format. Has a few bugs, but replaces CSpotRun, which doesn't seem to support the Sony hi-res fonts.
FileZ: File manager.
TimeCopy: Utility to synchronize the Clié's time with my PC. On the PC, I have a utility called Dimension 4 which synchronizes its time with an atomic clock. I still show up late for meetings.
Hacks (OS extensions): I'm using X-Master as my hack manager, FontHack123 and lubak's SansSerif22 fonts to replace Sony's thin standard font, and McPhling as a task switcher.