I just ordered a Rebel T3-i and I would like to know what type of SD card to get for it . Thanks for your help in advance.

Check page 288 of the manual that you can download here:

http://www.usa.canon.com/cusa/support/consumer/eos_slr_camera_systems/eos_digital_slr_cameras/eos_rebel_t3i_18_55mm_is_ii_kit#BrochuresAndManuals

It supports SDXC, so any cards labeled "SD", "SDHC", or "SDXC" will work.

Prices have come way down in the last year. You'll want Class 10 for dealing with large images and HD video. I feel the best deal is a 16GB card, but 32GB is best if you are going on a longer trip or shoot a lot without card changes. I have a 32GB in my 60D.

I'm economical and my favorite brands are 1) Kingston, 2) Transcend 300X, and 3) Ridata. I've had good results buying cards on ebay (look at the feedback percent).

I've bought Transcend 400X SD cards as the "2nd" spot for my 1D3.
32GB was 39.99. Compared to what I pay for CF, it was a steal. That was class 10.

http://www.amazon.com/exec/obidos/ASIN/B003VNKNEG/ref=nosim/deals000-20

Go with class 10.