OpenStreetMap is a work-in-progress mapping website / interface that aims to produce an entirely free (as in speech) set of maps of the world - thus they can be used on our wiki without having insurmountable copyrights issues that might be the case with other sources. The maps are contributed by regular people. Unlike things like Google Maps, OpenStreetMaps are freely usable by anyone for any purpose. All the software that powers the site is freely licensed as well. For these reasons, it's been considered a potential option for wiki mapping at some point in the future (read more here if you're interested).

The Corvallis map coverage seems pretty good, but as always, it is good to check: is your neighbourhood accurate? If not, you should fix it.