KFU EazyE for one of the best suggestions to post. Sometimes, I feel that all new posts should automatically receive a "Have you Googled your question" response.

KFU nimra for your avatar. Love it!
My apps of preference (check the downloads section or Google [tip: add treo to your search term of help limit results], hyperlinking everything is just too time consuming):
Neat Freaks Pack: Northglide's Cleanup and Uninstall, which keeps my Treo neat and tidy when I uninstall apps no longer needed/wanted. A must have.
zLauncher: Keeps my Treo and apps organized and purty lookin'. Powerful little program.
Warden: security - lock the Treo, remotely lock the Treo, remotely wipe the Treo, etc.
Agendus: contacts, calendar memos, travel planning, keeping my life organized
Agendus Mail SSL: easy setup (esp. for Gmail), multiple accounts, multiple folders, syncs with Outlook, stable on Treo, fast, can save messages to card.
BuzzOff: block callers with no caller ID or blocked caller ID (very handy a couple of months ago when Sprint marketing kept repeatedly calling their customers to sell crap), block certain numbers, block at certain times of day, only allow certain contacts to call
Resco Backup: backs up to my SD card every night
Backup Buddy: backs up the Treo and SD card to my PC every night
Splash Wallet (includes, Shopper, Photos, ID, and something else I deleted): shopping lists (very handy), photo management, IDs for banking, logons, etc. (can be run from the card, so the data is not on the Treo)
Butler: Key Launcher - you can launch all your favorites from any app using the shortcut you assigned in the favorites screen; LED control (it does a whole lot more, but I stumbled across it late in the game).
Scrabble: To help me forget about the loudmouths talking on their cellphones on the bus. Hooray!