I must put in a good word for Ajar Productions who have created a Flash plug-in called SmartMouth. Even though I use Flash less and less these days, I know what a time-consuming pain it can be to manually synchronise dialogue with animation. If you’re a Flash user, you’ll value anything that saves time, alleviates some stress and generally helps with the process.
If lip-sync is a major part of your work, whether you’re a studio or a freelancer, you might wanna check it out at Ajar Productions. I also recommend watching the video demonstrations to get a feel for how it works and whether it can fill that particular gap in your workflow.