Sell some secondhand thing, put it out on craigslist or similar in your country and sell it, but ask to be paid in bitcoins.

Lots of people will see this and start to think about what bitcoins is and how to get them, it will quickly spread the fact that bitcoins are acceptable.

I break this out from the guerilla marketing thread since I think more people will read it here. This is something everyone can do today.

It will really get peoples attention if someone sells their car for bitcoins or something expensive.

Bitcoin guerilla marketing thread.
http://forum.bitcoin.org/index.php?topic=27450.0