you'd be better off thinking about buying a new lens over a new camera body since you've only got the kit lens at the mo
if you want something inexpensive I'd recommend getting a nifty fifty... it's cheap, plastic and a prime lens (so you'll have to zoom with your feet)... and yet its, in some senses, one of the best lenses cannon make. You can get some really nice sharp images, you can shoot in low light conditions without having to ramp up your ISO settings, you can play around with the wide aperture/shallow depth of field....
http://www.amazon.co.uk/dp/B00005K47X/?tag=hydra0b-21&hvadid=9550946709&ref=asc_df_B00005K47Xmore bang for your buck than any other piece of equipment you'll ever buy IMO