Couldn't agree more! If you start pending your money now, before you even touch your new camera, your bound to waste it on things you think you need or want, only to find out, there were better things you could have purchased. Get to know your camera 1st, and most important... just have fun with it!
+1.
I wouldn't go spending much money at this stage. Work out what you like doing and where you might want your photography to go. Find the limitations of what you have, and move forward from that.
Bad advice that's been given here so far:
1. $16 tripod. I have one of these. It's crap. It's cheap for a reason and the last thing you want is a £600 camera sitting on top of it. I had one for a few weeks and it was totally untrustworthy and not very stable. Got good at catching the camera falling off.
2. $200 tripod. Work your way up to a $200 tripod if you want one. I put together an old Velkin tripod off Ebay for £9 and coupled it to a Manfrotto head that I already had (£40). Brilliant tripod for a fraction of the money.
3. Prime lens - eg the 50mm f1.8. It's a bargain of a lens, really is, but a really difficult lens to use. 50mm is already covered by your kit lens, so the only other thing is f1.8. Which is great but just difficult to use unless you are in the right situation. By all means get one later just to say you have it (it's a rite of passage), but don't get sucked in with "it's the greatest lens ever" BS.
However, what I would suggest as a great first buy is a Cokin P series with an ND8 graduated filter. (Or equivalent if you can't get Cokin. Don't worry about the Lee vs Cokin thing at this point. And buy P series as it's a good investment for bigger lenses in the future.).
Buy branded filters, not cheapies off Ebay as there is a big difference. Branded stuff is made properly, cheap stuff is vinyl on a bit of plastic.
The ND8 Grad will bring tone and contrast into the sky, which in turn allows the camera to expose the ground better, which in turn brings in more colour to the photograph.
Finally, buy an optical lens cap (Skylight, UV etc). When you drop a lens you will learn why.