Which app is the best for the LG500, for free international texting?
I don't know what the "best" ones are. This is the one I found that seems promising:
It's appears to be free only for local SMS or if the other person also has it installed. However, the rates for international SMS seem pretty reasonable.
There are a couple of apps when you do a search that appear to promise free int'l SMS but I haven't tried them.