In addition to HEM, I also use the following:
Table Ninja - worth it if you multitable (6 or more) on PokerStars
or on Full Tilt - doesn't work for stud games fwiw.
Table Scanner - worth it if you have a lot of hands on the players you play against, and if table selecting is important. i.e., worthless for 5nl, since table selecting isn't very important at 5nl, no matter how many hands you have on the other players.
Leak Buster - worth it imo, time intensive though.
Haven't used the others.
All these tools are allowed by PS and FT.