Nikon D5000, Canon 500D/T1i, Olympus E-620

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I have been interested in photograpghy for a while now and have just recently been able to afford a DSLR I have saved up around $800 and had my eye on these three cameras Nikon D5000, Canon 500D/T1i, Olympus E-620 I am most interested in macro, landscape, and nature (animals) photographs so i was wondering which camera would be best for those situations and if there are any other cameras within the price range that would possibly be better. I would also like to know if anyone has used these cameras and and what the pros and cons of each are i have studied them online and read a lot about them but i think someone with actual personal expirence might know something i dont. Thank you for any help