Well, for starters.. if the 28 or 35 are out of your budget, then a decent quality flash is as well - personally I wouldn't recommend anything below a 430 EX ii for a flash, but it comes with a ~$250 price tag. You dont necessarily need that much flash though; you could get something like a EX 270 for the price of a 50 f/1.8 (~$120); its' more powerful than the built in flashes on the rebel, and the 270 can be angled up for bounce, which is a pretty big deal, but you'd still want to get a diffuser for it so you'd want to add another ~$10-20. That being said, I personally
would go with the 50 f/1.8 and a pop up diffuser (if, again, you test it out and think you can work with 50mm all the time), but either option is viable and well worth it.
Adorama currently has the nifty fifty (50 f/1.8) on sale for under $100 (special online price from twitter):
Pop-up diffusers I would recommend:
Actually, this whole kit is pretty great (Fong pop up diffuser, and a bunch of useful stuff - microfiber cloth, blower, etc)
A couple more considerations:
A) Any hot shoe flash made for Canon DSLRs should work on your hot shoe without cables, and most will work pretty much automatically (feature E-TTL, or Through-The-Lens) metering. Even some third party flashes would be fine; you can save alot of money that way, but you really need to know how to (potentially) operate the flash manually (dialing in the correct power, etc).
B) The 50 f/1.8 has other great characteristics other than just letting in alot of light. In situations when there is enough light to open the lens up towards its widest (f/1.8), you can get nice bokeh out of a low cost lens (bokeh being the background blurring presented by opening the aperture all the way up and closing down the depth of field). I apologize if that's over-simplifying and you know what Bokeh is but in case you dont, just google 'bokeh examples' and check out some of the pics. It can be used artistically or to create a good deal of separation from your subject and its background.
Check out the guides listed in the stickies. I do alot of browsing on Photography-On-The.net, so I might be getting slightly confused, but I believe that either DreamKiller or R31ncarnat3d go over flash in one of their tutorials. Also, there's a thread about camera systems that might go into hot-shoe flashes. There's definitely a wealth of information here, hopefully some of us put it together in a way that's useful for you. And I know you've been around since August, but welcome to the photography section here at OCN! Edit -- no, Nikon flashes wont (standardly, at least) work on a Canon
. Here's a list of compatible Canon flashes (currently offered by Canon, there are a few others, like the 550EX, 580EX mark 1, etc) and their prices from Canon:
Canon 270 EX - $159.99
Canon 270 EX ii - $169.99
Canon 320 EX - $249.99
Canon 430 EX ii - $299.99
Canon 580 EX ii - $499.99
The first two digits of the model number are the guide number (number of feet for effective flash, but google 'Guide Number' and read up). As you can see, the more powerful the flash, the higher the price.Edited by MistaBernie - 11/14/11 at 8:28am