The method I came up with is speedy and pretty effective. I just have one symbol of a mouth with teeth. Draw it open as if it were saying something. To animate it, I follow the sound clip. (to make things easier,. put the sound for the character next to the mouth layer on the time line, this makes for easy synching). Then I reshape the mouth and flatten it, as if the mouth were closed. Copy this frame and paste it on your timeline at every spot that is "between words" or when character is not talking. Now insert keyframes at every "syllable" on the timeline. These you can just reshape according to the sound. For example an "oooh" sound you would push in the sides of the mouth and open it to make it look round. If youre looking for a fast approach that does the trick, I highly recommend you give this a shot. e-mail me if you have any q's on this.
Also, (shameless plug),
See it in action here!!
http://www.geocities.com/dolemite50/gd2.html