It amazes me that half of the electronic guru's in the world have never heard of or used this stuff. However, just about any TV repair or other workshop that does solder rework will have a tin of this by ever soldering iron. A 2oz can is going to last you at least 5 years. I think the second most important supply is solder wick. If you have ever made a mistake during assembly and needed to remove a part, solder wick is for you.
Solder wick looks a lot like coax cable braid.
When you heat it along with your solder, it will tend to suck all of the solder out of the joint. This is great when you need to remove a part from a circuit board. I recommend something in 0.060-0.085 width range. This will last you quite a while. If you use a lot, then I suggest Digikey or Mouser.