Just like HAM radio enthusiasts (of which I am one, by no coincidence), photographers tend to be whores for equipment. If there is one thing that's more exciting than actually taking pictures, it's buying all the equipment you think you need before even going out there. Some call it “retail therapy,” which is a deceptively medical phrasing for “it feels really good to buy stuff, and I enjoy feeling really good.”
Whether you need this junk or not is a completely different question, and one that I could certainly answer for you, but I doubt you'd listen to me. Who am I, anyway, other than another guy who loves buying stuff he doesn't need?
You know who you should listen to? Scott Bourne.
I've been writing this blog for a little over five years now, which seems like a long time to me, but Scott has been writing about and teaching photography for six times that long (yes, thirty years), so he deserves your attention for at least the next ten minutes… Which is all it's going to take you to breeze through his newly updated DSLR Camera Lens Buying Guide on Photofocus.
Within the Guide, Scott offers tips for choosing what to buy and gives examples of each basic type of lens in both Canon and Nikon flavors.
For all of you Sony, Panasonic, Olympus, and Minolta shooters out there, don't worry… I'm sure there's another blog out there for you guys! Ha ha!
But seriously, these are good tips and you should listen to what Scott has to say, he speaks from immense experience.
Scott Bourne's DSLR Camera Lens Buying Guide via Photofocus