Gbridge is a free software that lets you remotely control PCs, sync folders, share files, and chat securely and easily. An extention of Google's gtalk service, Gbridge automatically forms a collaborative, encrypted VPN (Virtual Private Network) that connects your computers and your friends' computers directly and securely.
The plugin also adds a few new convenient features to Gmail related to follow-up messages. If you have a particular issue that you need to keep an eye on, you can opt to send the message and have Gmail remind you if you haven't heard back within a specific period of time. It also adds a category in your left sidebar for all messages awaiting reply, so you can view them all at once if you want to.