Good Lists! I would ABSOLUTELY have to have the following, freewares first:
DateDifference
Offstroke
ScreenButton
TomCatalog
Files
sysTool
Paid Software:
AcidImage
Bonsai
CardBackup (jkware)
TealMover
TealScript
TealDoc
TealLaunch/Master
And, of course, the Docs2Go that comes packaged on many P1 handhelds. By using TealDoc with a freeware desktop interface called TextSync from SourceForge.net, you can skip both Word 2 Go (Dataviz) and WordSmith and actually do MORE.
Many of the freewares available are BETTER than commercial stuff and a very small footprint - screenbutton combined with TealLaunch (1 free, 1 paid) is the best "launcher" you can have IMHO; offstroke is great for fast "off" and something like 2k in size. The TextSync "stub" is less than 1k.
What you save on the freewares can help finance the PAID stuff, but if you DO DROP $150 on GOOD paid stuff, you'll have the handheld from hell if you combine it with the free.
We now start to get in to "variations" of the lists based on personal choice; MANY of the apps mentioned in above two posts are EXCELLENT but people differ - some like SplashID, I'd go with TealSafe/TealLock. Some like ShadowPlan Outliner, I like Bonsai. Some like AcidImage, some like RescoViewer; it's all personal taste. However, these lists will give you a general idea of things to look at, and you decide what's best for you.
I happen to be a "file uitility" freak and so I have SysTool, Filez and TomCatalog (all free), but TealMover does some stuff none of them will do (and vice versa). Net result 4 file managers! You may not be that "picky," but talk about having control!!
Last thing to think about would be JackSprat/JackFlash and THEY are a VERY personal decision; do ''em "incorrectly" and you've got a paperweight! However, if you're going to keep music on the handheld and NOT the SD Card, I'd recommend "making the leap" and putting almost ALL of the above listed apps (EXCEPT: CLIP PRO, TEALLOCK, TEALLAUNCH, and TEALMASTER!) in flash and you'd have almost 100% of RAM free for your music or other stuff. They're also protected from even a hard reest, as long as you remember to load JackSafe first upon initializing the flash. I realize JS/JF is a whole separate discussion, but I'm running 52 apps and 5 libraries and have 95% free of RAM. I also only use 2MB per backup file on the SD Card, and since I maintain TWO backups, I only use up 4MB on the card. If you had 12MB in RAM and made 2 copies of it, you'd be backing up for a full minute or more x 2 files, and load up 24MB on the card. Think about it -- that's around 8 mp3s combined with a VERY quick backup time (my CardBackup process averages around 4-5 seconds per file).