OGDev -
A couple weeks ago I hacked support for Geocoder.us into OpenGuides. Admittedly, this is only useful for US guides, but it has made my life infinitely easier when adding guides - before I was keeping two tabs open and checking out Geocoder for each address, now that's taken care of in the backend for me.
I'm merging my forked version of 0.47 to 0.51 today, and this is one of the changes that other people running US-based guides might want or need. I've attached a patch. It's not the cleanest solution in the world, but it's something.
It should merge nicely against most versions, since the code surrounding it hasn't changed much.
I don't know if this is desirable for the main branch, simply because most of the guides right now can't be helped by it at all, and the code is simplistic enough that it could be reproduced by anyone with a small amount of effort. However, it's here anyway.