I love Motocast. You just download the server software on your computer, and during setup select what folders you want to share. I'm able to stream DVD-quality videos over 3G, and 1080p HD movies over Wireless or 4g. I have both my wife and my Razrs attached to my home computer, it's a nice way to share music, movies, documents, whatever you may have on your computer that you'd like to have remote access to.
I've also discovered Google Music which is a nice way to have cloud access to your music collection (better than carrying 10 or 15GB of music on your SD card); Motocast seems the best way I've seen thus far for large videos though.