I'm a little late to the party but I wanted to chime in. Those are some great shots, man! I've got a Canon T2i and it's a really fun camera. The kit lens isn't as bad as I was expecting but you gain a lot from better stuff. If you haven't looked at it already, check out the 50mm f/1.8. It's incredible for the price (about $100). It feels kind of cheap but very useful and quite sharp. It's the only extra lens that I have right now but I'm looking at a 28-250mm f/3.5-5.6. It's a little pricey but there are some good deals showing up on eBay. I'm still exploring my options, though.
How do you like your 55-300mm? You mentioned shooting some soccer games; is that the lens you use? Is it fast enough to keep up with the action?
In regards to post-processing, you should check out
ArtWeaver. It's free and does quite a bit. It was my go-to editor up until I bought the Adobe Creative Suite through my school. ArtWeaver is arranged in a similar fashion to Photoshop so it makes it moderately simple to make the jump up to the Adobe suite. There are other options but ArtWeaver really impressed me.
If you want something that you don't have to install, Adobe actually offers a
dulled-down, online version of Photoshop. I haven't had to use it on my computer but I have used Photoshop Express on a tablet and it was pretty nifty. It should be enough to get you off the ground and do more than the integrated Windows editor.
It's been a few months since this post was made. Do you happen to have any updated photos? It'd be cool to see how you've progressed with the camera over the last two months.
Either way, keep having fun with the DSLR! Your shots are looking good so far. They're
way more fun than any point-and-shoot camera I've ever picked up.