As you may already know url shortners are nice and easy way to track how much traffic is coming to your web page from specific location(s).
If you don't know about url shortners this is what is all about - If your web address is www.yoursite.com you can go to some url shorting service and put your web addres there and it will give you link like bit.ly/wetwf
Than you post your links online (facebook, twitter forums, blog comments...) and on url shortner site you can see how much clicks you get over your shorten link. This is how you can see what traffic sources work best.
Here are some popular url shorting services:
bitly.com - very nice and easy
su.pr - service from Stumble Upon(they say that it can increase traffic)
goo.gl - this is Google's service
awe.sm - This one is not free. It is 30 days trial and than $15/month. I didn't try it but they say it can track conversions also
What services do you use and what are your experiences?