Can anyone recommend a good flash unit for my Canon Rebel Xs? I'm sort of on a budget and can't afford the $500 Canon flash, but I would like something where I could point the light at the ceiling, ect.
Is there any other good places to buy used camera equipment besides ebay, adorama, or B&H?
I don't know if adorama or B&H do second hand goods (I don't deal with them as I am in the UK) but they are reputable dealers (and one if not both even have reps as members here) so I would be willing to trust second hand goods from them
As for Ebay = its your risk really, some people are worth dealing with and others are not, so stick to known good sources and people with high good ratings (Also take the time to review the bad ratings on a person account - sometimes they might be nothing more than slow postage -- something to be aware of -- othertimes they might show that certain products have a higher fail rating than others).
With second hand goods I would always want to try before you buy - with reputable dealers (eg Adorama+B&H) they do test the gear for you and its in their interest to report on its actual functionality.
Haven't used it personally, but my photo buddy Ed just bought two Sigma Super DG 500s and swears by them. They are fully compatble with ETTL Canon speedlights and can be used as master or slave units. In Canada here they are only $269.00 CAN$$. Same or better power than the new 580EX lls