HOW TO unlock your Nexus One and turn it into a 3G modem. I think you can do something similar with a Motorola Droid, too. It would be better, though, if they shipped with this feature, as some other cellphones already do.
UPDATE: Reader Fred Schoeneman writes: “You might want to clarify that those instructions are for linux. For Windows users, tethering your Nexus one is as simple as installing an application from the Android market — PDANet.” I did not know that. Makes me more likely to upgrade to a Nexus One.