Wifi Manager by Kostya Vasilyev is pretty essential for me, one of the best interfaces of all the wifi finding apps out there. But then, I'm a filthy Canadian, so every kb of data up here costs exactly one reek-ridden prostate punch by studded gimp (Family Plan).
I use Astro File Manager for navigating and moving files around. Highly recommend.
The Swype keyboard is lightyears better than the native Android keyboard once you get used to it, but by the time I went looking for it, the app had been pulled (I think it was in a limited beta). I managed to find the apk file that someone uploaded after a bit of hunting on
http://www.xda-developers.com/, (which is a pretty handy site to have bookmarked for any Android development news, as well as having everything sorted by platform/model) and I'll gladly throw a few bucks at it when the final goes live. If you're interested and have trouble finding the apk file, pm me.
And finally, I use the AppBrain market app. This is just a handy way to see what's new or hot on the market without trudging through the previously-griped-about hundreds of junk apps that get tossed up every day. Helps make the decent/interesting apps stand out that you might have scrolled hastily by after viewing the fifth page of "Hot Sexy Girl" apps. Doesn't replace the default market, just provides a nice alternative.
