If you've got plans to keep your Canon T2i powered up longer than the normal battery can provide, here's a cheap AC wall adapter. Great power source for taking those super long day to day timelapse photography shots. If you're the daring type like myself, the battery adapter provided is perfect to hack up into a DIY Power pack, perhaps connecting it to something like a Radio Controlled toy car rechargeable battery. You can find several aftermarket AC wall adapters here: Canon T2i / 550D AC Wall Adapter Power Plug

For those running the LP-E6 battery type like the Canon 5D Mark II, Canon 7D, or Canon 60D the AC wall adapter can be found here: http://cheesycam.com/a-diy-canon-dslr-power-pack/