This list got much longer than I had expected. I started off quite a while ago just bookmarking Star Wars parody t-shirts when I came across them and just before I was about to write this post I decided to check to see if I had missed any good ones and discovered that I had. I also discovered a similar post at Tcritic and admit to grabbing some of those t-shirts too. This seems like a pretty comprehensive list of Star Wars spoof t-shirts but I know there are many more out there so if you know of any just add a link in the comment section and I will update this post if the design is suitable.
There are a huge number of t-shirts at Zazzle which sells officially licensed goods for Star Wars and it would be impossible for me to list them all but if you find one that warrants mention feel free to link to it in the comments.