You can try making your own shoulder mount if cost is an issue (Pro stabilizers can cost a lot of money):
Other video equipment that I would recommend:
At least 3x batteries
16GB+ memory cards
Audio Recorder (Zoom H4n or Tascam DR-100)
VideoMic or Sennheiser on-camera microphone [not 100% sure that the Sennheiser fits onto the T3i]
Prime / Constant Aperture lenses….
1) Old Nikon Lenses (I'm looking into the 20mm F2.8, 24mm F2.8, 28mm F2.8, 35mm F2.8, 50mm F1.4, 85mm F1.8, 105mm F2.5, 300mm F4.5, all non-AI)
2) Canon EOS Prime lenses (28mm, 50mm at least)
3) If you have the cash, the Tokina 11-16mm F2.8 lens is great (but is a crop lens, so it won't work if you upgrade to a 5D)
Tripod with fluid head, reversible center column, and a maximum height of 5+ feet. I'm currently considering the Manfrotto 055XDB with 501DV Head.
Monopod.
Grey/White balance card.
Lightmeter.
Glidetrack SD.
Battery Grip (Vello makes one that's cheaper than Canon's)
Circular Neutral Density filters for lenses.
Viewfinder of some kind. The best is the Zacuto Z-Finder (Has a diopter), but it's expensive.
That's what I have for now [posted some other thoughts a few pages back]. I'll update if I think of anything else.