What program do I need to open raw images from my EOS Rebel T2i?

[RobertTheFat]

The obvious candidate is Digital Photo Professional, Version 3. It's free and should have come with your camera. If it didn't, you should be able to download it from the Canon site.

There are various other photo editors as well. One or two of them have strong partisans in the forum; I'll let them regale you with the advantages of each.

[jrhoffman75]

Bob is right on. Since you are asking the question I am guessing you are a beginner in this area. DPP is free and does the job.

There are several programs that do more, but they cost money.

After you have used DPP a while and become comfortable with RAW capture and processing you can download trial versions of some of the pro-level products (Lightroom, Photoshop, DxO, etc. and see which of them you might want before you pay.)

Here is where you can get latest version of DPP:

http://www.usa.canon.com/cusa/support/consumer/eos_slr_camera_systems/eos_digital_slr_cameras/eos_re...

[ebiggs1]

Although not a big fan of DPP, I too, urge you to start with it.  Later you can try the better offerings.  You can't argue with free!