Hi Fuzzylemurs,
I was in the same boat as you a few months ago. I bought the 500D (T1i) in November and had a lot of questions about lenses, filters, etc.
First off, I agree with everyone here who has suggested investing in some good glass. A good quality lens will make all the difference to your shots, the enjoyment you get out your kit and the creativity that flows from there. Also, don't be afraid of third-party lenses; they can be a really great option.
A decent, fast zoom for "walkabout" photography would be my first suggestion. When I bought the camera, I tested out the Canon kit lenses in the store, and at the advice of the shop assistant and a very good friend, opted instead for a Tamron 17-50mm f/2.8 (not the stabilised version). It's a brilliant lens for the money and a fantastic upgrade from the Canon kit options. It does have a couple of drawbacks (a slow and noisy zoom being the primary one) but I'm really happy with the purchase.
I quickly realised that I also needed a decent telephoto zoom. After a couple of months of reading reviews and playing around in stores, I settled on the Canon 70-200mm f/4 L IS. It was definitely a big investment for me, but I couldn't be happier. I've had the lens a couple of weeks now and I'm having so much fun with it, and I'm getting so much more out of the camera because of it.
Both lenses have B&W MRC UV filters. For me, the issue wasn't dust or dirt on the front element, but the fear that clumsiness might get the better of me and that I might accidentally scratch or seriously damage the front element of either lens. There's a lot of debate over whether or not filters are a good idea, but for me it was about protecting my investment. But DON'T cheap-out on filters. An extra $40 spent on a filter for a $1200 lens is well worth it.
Best advice from me, as a lot of others have said, is to get out and shoot, whatever kit you're using. Stick with what you've got for a few months and from there see what you'd like to invest in. Maybe you'll be hooked on portraiture and want a set of fast primes (I love the Canon 50mm and 85mm f/1.8 lenses - both brilliant for the price, and I'm about to go buy the 50mm). Maybe you'll want to try your hand at macro nature work (you should try to borrow the Canon 60mm macro from somewhere - it is a really fun lens to play with). But play around, see what you're into, and let your kit slowly evolve as you learn what it is you enjoy.
Hope this is helpful. Happy for a PM if you've got questions.
Peter
