Ok, this is really simple and it worked for me and my Linksys WiFi. 2 step is all it takes to explain to anyone how to fix this common problem.
Step 1: Find Your Router
Find you router. This is pretty simple but good luck anyway.
Step 2: Boy or Girl?
Now look at the back of your router...
...and locate the reset button. It's blue and set into the case...and says "reset" above it (duh).
Step 3: Lets Do This!
Now prepare yourself. Look around for a pencil...and use it to gently push the reset button.
Now you are done! all you have to do is go on you iPod Touch>settings>WiFi>Choose Network> and choose yours.
Bask in the glory of technological understanding!
PLEASE NOTE: THE PICTURES USED IN THIS INSTRUCTABLE ARE NOT MY OWN. IF YOU WISH TO SEE THEM REMOVED, I WILL DO SO IMMEDIATELY.