I'm going to check out Elixir, that one looks nice! I've been using widgetsoid and have liked it, but I like the look of the Elixir icons and the info it gives. And it's free, which is always nice!
I've recently become a huge fan of the GO apps. Go Launcher, Go SMS Pro, Go Weather, and Go Calendar I think are the ones I use. At the very least, get the Go SMS Pro and Go Weather. Those apps rock!
I also use LookOut which helps protect the phone from harmful apps (the reason you would want antivirus is because android is considered open source software, and anyone can make apps... and some apps can be dangerous which is why Google has yanked some off the market). It also has a backup feature and a locator feature.
I've also recently started using Netcounter to keep track of my data usage. Tracks both Wifi as well as Cell data.
FriendCaster is also an app I won't do with out. Use it instead of the official Facebook app. It's more stable and more user friendly.
I'm going to be following this thread as well. I'm an app junkie.