http://wiki.openstreetmap.org/ - Main site
http://wiki.openstreetmap.org/index.php/JOSM/ - Best offline map editor
Are you a fan of open source?
Are you a fan of wikipedia?
What about free maps?
You'd say that Google Maps are free, right?
Not exactly!
They are free for online viewing but they are copyrighted.
You cannot print a Google Map of your neighborhood and have it sent over to your folks so that they know how to reach your place.
It is illegal!
Moreover your kids can't use those Google Maps in their school project.
OpenStreetMap is an open source project aiming to produce free accurate maps out of free GPS data.
You go out for dinner and you take your PDA with you along with the bluetooth GPS receiver.
You grab the GPS data of all the streets and motorways you used to get there.
When you get back home you upload that data to your desk PC and then you edit it with JOSM to insert the street names and stuff.
JOSM can also upload your edited data to the OSM server so that you share your work with others.
Of course you don't have to do all this and you can go right ahead and take a look at your own city map already.
http://almien.co.uk/OSM/Places/?action=recent
Or if you can't find it on that list you can always search for it here
http://almien.co.uk/OSM/Places/?action=search.
Cheers