There is a book called Potty Training in a Day (Azrin). It has a great way to deal with accidents, and "practicing" potty training. It is time consuming (maybe 30 minutes of practice time after every accident), but my daughter doesn't even get a little pee on her panties... I can never tell by looking at them if they are clean or dirty.
This is the basic practice sequence:
1) Talk to her about how nice it is to be a big girl and be clean and use the potty... express disappointment that she didn't be a big girl and hurry to the potty when she needed to use it... express confidence that she will be a big girl next time and say, "We're going to practice to help you potty like a big girl."
2)Choose 10 different areas of the house where she might be playing and do the following in each area (I'll use her room as the example).
3) Say something like "Okay sweetie, pretend you are playing in your room with your dolly. You're having a really fun time and you don't want to stop what you are doing. You realize you need to go to the bathroom. What do you do when you need to go to the bathroom? You don't wait, you hurry to the bathroom as fast as you can... let's practice... Put the dolly down and let's hurry to the bathroom"
You then hurry with her to the bathroom, have her remove her pants and sit on the potty as if she is really going to go, then redress and wash hands. Repeat the sequence several times, 7-10. She will realize really fast that it's more fun to play than practice pottying for a long time after an accident. It reinforces how important it is to hurry to the potty when you need to go.
We did not use this method with my son (now 5 1/2) who is 18 months older than my daughter, and he still has a lot of near misses and lots of pee spots on his underwear... I need to do the practicing with him, but I haven't done it because I have a nursing infant and the 3 of them keep me Sooooo busy. : ) Good luck E.!