Does anyone know what chord it is best to leave off on without resolving it near the end? (I.E. instead of a normal resolution such as V to I or something, leaving it off on a IV or something...) I've noticed that quite a bit of songs do this now-a-days and was wondering what chord would be best to use for leaving unresolved @ the end... Bach often did this in his suites until the final movement.

I would try either a suspension/anticipation chord, or a 7th chord. I use 7th chords a lot in my work.

I actually add a note to the chord that adds stress to the end. (don't know the name of it, though)

usually adding in another note adds an interval name, such as a 6th or 2nd. Combining two entirely different chords (such as G Major and C Major) can be a good idea also, (this also can be called a C major chord with an added 7th and 2nd).

V-vi or (or V - VI in a minor key) is what textbooks teach us, and you should stick with only that for now. It has been stated that this form of cadence can end with basically any chord, but I don't think you're ready to try others yet..

This cadence is called a deceptive or an interrupted cadence.