Ask.com Maps and Earth
I've been playing with Ask.com Maps (use Firefox or Internet Explorer; Safari isn't supported) for a few weeks now and I've been pretty impressed. It supports several features that Google Maps doesn't (multiple waypoints, walking directions, right-click support to add a waypoint right on the map) and it has no ads. Inspired, I decided to map a trip from Pittsburgh to Anchorage. That's about 5,000 miles according to a former coworker from Alaska. It was going along just well, and then...
"Turn Right continuing on Alaska Hwy for 17,150.2 miles." The total distance, dominated by this one space-time discontinuity in the Yukon Territory, is over 20,000 miles. Ask.com thinks it will take me about 21 days of constant driving to get there.
My only theory about why this happens: at some point Ask.com's mapping logic must think we're going all around the world at that point. The map itself shows a map that looks driveable if you don't mind an extremely desolate trip west-northwest through Canada.
Incidentally, Ask.com is still ahead of its competition: Google won't even offer any directions to Anchorage from the lower 48.