I tried a new tool with Kyle Shipley recently, and it has proven to be interesting and useful.
Floobits is a recently-created remote pairing solution. Imagine wanting to pair with someone and they are across town or in another state.
I enjoy pairing remotely, as it lets multiple people work together even when they are not colocated. I think that pairing is a great way to share knowledge on a team and reduce defects by promoting accountability and quick feedback. Further, I think that remote worker morale increases when talking and working with teammates.
Kyle and I used Floobits to pair on a random coding project, and I found the entire experience compelling enough to get past the set up and some early wrinkles. With Floobits, you create a shared workspace that other people can view (public or invite-only). You install a plugin to your editor and maybe a custom build of the editor. Then when you make changes to the file, diffs of the code are sent up to a server, which then propagates to anyone connected.

Existing solutions
There are some solid existing solutions out there like sharing tmux or screen sessions.