Plex is the shizizzle.

Lifehacker have pretty much got this one covered so I'll redirect you to them and give them some love because they deserve it. For one they referred me on to Plex and I will forever be thanking them. For two I'm just really happy what Plex has done for my vast media library.

Lifehacker's Plex Article

Plex basically is a media centre to replace Front Row on the Mac (Sorry PC and Linux users) and does a very fine job of it. I'll post some screens of it below to give you an idea of the excellence.

It organizes music and photos, which is great and all but not something I would use the software for. I've got iTunes and iPhoto for that. The cheese comes in the organization of movies and TV shows. It completely shits on Front Row in what it does and I can only explain it to you in pics. So look below or go to Lifehacker's article.