I use Guitar-Pro. I've heard good things about AcuTab.

While Guitar-Pro is supposed to transcribe tab from one key to another (and does for guitar) it doesn't "understand" the special status of the 5th string, so it messes up the result of transcription. Even so, I've used it to a degree, limited mainly by my own lack of musical education, and have been pretty well satisfied.

I know there is at least a third tabbing program around, but can't think of the name right now.

Dave Oesterreich