Now at my previous job we wore just about anything we liked. It had to appear neat and not cheap and that was about it (as can be seen in this picture that I took on the last day of my job with VLS, work wear could be adventure/trail wear).
So to me the idea of wearing formal clothes is pretty alien. So I turned to my trusty friend Google to provide me advice regarding what I could wear to work. And here are the two links I found that best explained the finer sartorial points of "business casual" dressing:
Career Services at Virginia Tech: In simple terms explain what is ok and not ok at work.
Sartorish.com: If the name doesn't say it all, this site goes into the finer points of looking good at work.