How can I screen share into a remote coworker's Mac? I have a coworker who should do some testing on a Mac but is a Windows user who has no desire to learn the Mac. If I could just log in to his Mac, which is on a wireless network, and do his work for him I would be so much better off. I am about 2000 miles away from him, however and we are not on the same network (it's a small company).

So...is it possible to remotely take over his computer by enabling remote administration in Settings, without being on the same network?
There is a long list of options, I'll just mention a few


you can both set up an iChat account and use screen sharing there
both parties can install (and log in to) Skype which provides screen sharing as well
install TeamViewer on both machines


In your situation I would probably go with the TeamViewer option.