Here's the ones I've heard of or commited.
Make sure all your links work especially to affiliate programs from PPC engines otherwise they get the sales that you paid for but you don't get the credit.
Don't buy e-books on Internet Marketing. Everything you need to know is available for free on this site.
Focus on one program at a time. Automate everything. When it's successful move to the next program.
Make sure to add alt tags to your images.
Goosh this could go on forever! You might have to separate it into categories like
SEO PPC Affiliate Design etc.
But I love the idea. I can't wait to read everyone's mistakes.