i know a lot of people go for settings to give them the best quality for file size but I am looking for best compatibility.
When I render the file I want to be able to play it on a windows machine and Linux. i just tried a render and the file didn't play back correctly on linux (using GnomePlayer) or Windows using Virtual dub. What are some good fairly standard settings for quite good quality and good compatibility.

I think that depends entirely on what codecs your player has available to it. VirtualDub is not intended to be a video player, and if I'm not mistaken it doesn't have x264 installed by default. Most of the default players on Linux also require you to download "suitable plugins" for many popular codecs. The exceptions are VLC and MPlayer, so try one of those. They will probably play your video.