Just to expand on what skirball wrote a little...
No Canon DSLR has internal memory to be able to take shots without a memory card. I can't think of any of the more recent point n shoot/compact cameras or other manufacturers' cameras that have internal memory either, these days. Some early digitals did, but not many (any?) I'm aware of in recent years.
Besides, memory cards are cheap! I'd estimate an 8GB memory card will hold well upwards of 300 RAW (the largest) files from your T3. An 8GB SDHC ("High Capacity") Class 4 10MB/sec might be fast enough for your camera. One of those costs under $8 on Amazon. For some future-proofing, you might try to get SDHC Class 6, 20MB/sec which is a better choice for some of the other camera models, although it costs a bit more. Class 10 is even faster (30MB sec write rate), and a bit more expensive.
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM
