Bow and Arrow, man. If you aren't good with one, learn to be. It'll save you from many spiders and creepers. I've gotten to a point now where a few days ago I was in our SMP world cave exploring, I was accosted by two zombies and a spider, and I killed all three without missing once. I. Felt. Awesome.
Seriously. Find a skeleton or a zombie spawner if you can, turn it into a mob grinder, get their feathers to make arrows, or get their arrows and bones, and fill up with about 2 or 3 stacks of arrows. This'll be more than enough. Each mob only takes 5 hits from arrows (each arrow does 2 hearts damage, each mob has 10 hearts). Just remember that every time you hit a mob, they are invulnerable for a second while they're taking that initial damage, so doing a volley of arrows just wastes ammo. One at a time, carefully aimed. They also are knocked back slightly. This can keep them in place with the arrows if you time it right.
Good luck, man.