I almost taco'd my rim recently. I don't know if this is good for you but this worked for me:
1. remove wheel
2. remove all spokes
3. clean it out since its off
4. place rim on flat surface to see if its bent
5. straight rim with hands
6. onces its pretty straight, put the wheel back together
7. true it
it worked pretty good and my wheel was in bad shape. im still using the wheel on the mountain bike trails and has survived alot