Free: Contests & Raffles.
I'd buy a Canon. Have always loved it. Nikon is as good I am sure. i would look at a 40D. 20D would work as well and save you some cash, but really a 40D has really come down in price. bodies are the cheap part. Then I'd suggest the 300 F4 lens. its about a 1000 right now and I'd pick up a 1.4 extender. That will give you the reach you need. or the 100-400 lens.
Where did you buy your 30d, craigslist ? Ive been having a hard time pulling the trigger on a camera.
I prefer Canon as well and I know there are a few guys on here that prefer Nikon. Hard to go wrong with either but one thing you might consider is the feedback and help. Not a knock on them at all but for some reason the Nikon guys don't post as much as the Canon guys, again not a knock but its true. You are likely going to have questions answered quicker from a Canon shooter for the simple fact that there are more of us and we post more info and pics. Another factor you might consider is if you get together with a group from here for a photo trip, swapping lenses to try them out is nice. Sure general questions can be answered but when it comes to specific operation of your camera, its not as easy when not familiar with the brand/model.