I have Verizon Dsl with a modem (wifi) and need to add security. My sons both have the Ipod Touch and surf the internet and get on sites that they should not be
Most routers will have a place where you can enter the address (or partial address even) of such sites.
Another option is to add/change your WPA password, and to not disclose it to your children. Be warned that this will only work within your home, and will not stop them from going elsewhere (such as Starbucks or Mcdonald's, anywhere with a hotspot, or even a friend's house) and accessing the same sites from there.
Another option, is to take both their iPods and enable restrictions, here's how you do it.
Touch "Settings" on the home screen
Navigate to the "General" tab
Scroll down to "Restrictions"
Tap on "Enable Restrictions", then enter a 4 digit passcode (you will have to do so twice, be sure to use a code they won't guess)
Slide the switch next to Safari to "Off"
Exit to the homescreen, the Safari button will now be gone, and your kids will not be able to browse the web on their iTouches. You can also disable other things in restrictions, as well as set other parental controls. They won't be able to bypass them.