Yesterday was a big travel day for us just getting from point A to point B and we really weren't interested in stopping until about 7pm for the night. So, we didn't want to pay too much for a camping spot since we would only be there to sleep since we were getting up early and hitting the road the next morning.
We found a website- freecampsites.net that directed us to the visitor's center in Eagle, Colorado so we tried it out. We called and asked if we could boondock overnight (camping without hook-ups) and they said yes. When we got there the parking lot was empty and was right next to The Eagle River! There was also a bathroom open 24 hours!
If you're looking for a free overnight spot on I-70 west just past Vail, CO the visitor's center in Eagle is great. By the time we went to sleep there were about 2 other cars in the lot that spent the night as well. Just down from the visitor's center is a parking lot for trucks to stay in also.
Yay for free camping with a bathroom!