Please don't "invest" in bitcoin.
If you are going to buy some, find some kind of project that interests you that you can use them for.
If you want to make a profit out of buying-> holding-> selling bitcoins, you can end up either euphoric and rich or downright depressed and poor depending on wheter you bought them on a peak or minimum. The market is very volatile atm, and as long as people hold on to their BTC it wil stay that way. Bitcoin needs to circulate to work.
If you buy some, there are a lot of cool things you can do with it though. Buying stuff at a cheaper price, paying your friends for goods/services, drinking a beer, starting your own project involving this revolutionary technology.
If you want to buy some you have a couple of options.
Online trade houses
mtgox.com
btc-e.com
Offline escrow service
localbitcoins.com
Or find someone you trust that has bitcoin and trade with them.