I use both 60/40 and 63/37 solder. I like the 60/40 for general purpose soldering. Tinning wires, desoldering, etc. I love the 63/37 stuff for fine soldering or high heat stuff because it goes solid much quicker.
I tend to buy my stuff locally as I live conveniently close to a local electronics store, and just picked up a roll of this a few weeks ago while buying replacement tips and other knick-knacks: