A few options for cracked iPod Touch screens not listed here:
1) You could always back up your data and get a new iPod Touch off of Ebay. Depending on the version and size, you could probably pick up a used one in good shape for as little as $120.
2) Apple offers repair services for the iPod Touch - including cracked glass. The cost depends on which generation you have and your storage. You can see a complete list here: Apple - Support - iPod - Repair pricing
3) As mentioned, you could buy the parts online and do the fix yourself. A quick search on YouTube for "iPod Touch Take Apart Video" will reveal all kinds of hits. Then go to Ebay and do a search for "iPod Touch screen assembly". I highly recommend getting the full assembly with the midframe and home button already in. It'll cost your around $25 but it will save you a ton of headaches. Trying to swap out the home buttons is a serious pain and not worth the effort. Also, make sure you get the right part! The different screens between generations are NOT compatible.
4) Lastly, if you don't feel comfortable pulling your phone apart yourself or paying Apple a bunch of money to do it for you, there are 3rd party options. In the spirit of full disclosure, I own a small company doing iPod Touch repairs
, but there are many other companies out there. A simple Google search might even reveal someone in your city that can do it for you in about 15 or 20 minutes. This repair should definitely cost you under $100.