In my workplace, I get the usual free stuff that everyone mentioned above. Here are a few more...

Almost everyone of my coworkers drink coke or pepsi. I collect all the bottle caps for coke reward points and pepsi stuff points. Also, dr. pepper, ect. It only takes a few seconds each day and you can collect points to get some cool free stuff every few months.

I bring my car trash all the time and throw it out at work. I always keep a plastic bag inside my car and when I head to work, I quickly collect all the trash and than take it into work tied up and toss it. It keeps my car clean.

I work at a salon and I borrow cd's at the end of the day and burn copies of them. Than I bring it back to work. As long as the owner/manager is cool with it, that might be something you can do. Anyone who works at a place that pipes cd played music, you can bring your laptop in there and use it to burn cds.