A few of the guys on here use the sonys. Most are Canon with a few nikon users
Main things to look out for are number of aftermarket lens avaliable. Nikon and Canon both have the most.
Mega pixels are only a marketing tool. You can print A3 size pics from a 3mp camera
Also go to a shop and see how they feel in your hands! No point in using a camera if it dosn't fit your hands or feels odd.
Canon
****d are the very basic
***d are enthuastic
**d are semi pro.
If you can strech to a *** series camera go for it. They have better senors and build quality.
Nikon are similar d3000 cheapest to d7000
Adam is right about the lense but at the lower end of the scale they are all about the same. Only when getting more glass does does it pay to spend a bit more.
Out of the above i'd go for the 500d but you may want to budget for a telephoto in the future for track pictures or anything far away.
A get you by lens could be
http://www.amazon.co.uk/Canon-75-300mm-4...9825&sr=8-2http://www.warehouseexpress.com/buy-tamron-70-300mm-f4-5-6-di-ld-macro-lens-canon-fit/p1013817+ remember you will need memory cards, case and possibly a spare battery. Does that all need to come into your budget?
Most of the pictures on my flickr accout were done with the kit lens.
And these with the canon 70-300
http://www.flickr.com/photos/micky_photography/sets/72157624534600536/If you are on a tight budget maybe consider a bridge camera? Dslrs require you to put effot in to get good results. The main reason for going for a dslr is to take more control on how you take a picture. shutter speed, aperature control, no delay when you push the shutter ect.
If it's just better quality pics most recent brige camera can match a dslr for image quality.
Hope thats help out a little and isn't too confusing