You could try QuickReply for SMS. I think it's only a couple bucks. I absolutely loved it. Most prefer iReal or Bite, but Quick was my favorite. Unfortunately, I had to remove it because it was causing safe mode crashes daily. I heard an update fixed those problems; it also could have been conflicting with another app on my phone.
- 3G Unrestrictor (sort of useful but I don't YouTube or App Store a lot off of Wifi)
- Cyntact (more pretty than anything)
- iFile (though I'm starting not to use/like it)
- Elert (very useful - e-mail preview overlay)
- HapticPro (LOVE THIS!)
- qTweeter (awesome for Twitter/Facebook fans)
- YourTube (meh.)