This is probably not new information for most of you, but I just found out about a site called GeoChecker.com.
I personally would like to see it used on more puzzle caches, so that people can check their coordinates before heading off to a cache. Not all of us can do these caches with accuracy right away!
It's very simple to use and put on your cache page. The only hitch is that the person posting the cache has to enter the correct coordinates on the site first before you can check them! In other words, unless they have linked you to the site, you won't be able to use it for that cache.
I just used it on my puzzle cache, though I didn't need to because it was easy! (Just wanted to try it out.)