For your ISO burning question, K3b comes to mind first. Although it is a KDE program, a lot of people still use it in Gnome. It is the most complete burning program for Linux. It you want a native Gnome app then Brasero will do the job.
I highly recommend VLC as a video player. It will play all the formats without requiring extra codecs to be installed. I recently switched to it because none of the other players would consistently play all of the videos I wanted to watch. I'm actually planning an upcoming blog post about it because I've been so impressed.