Some sites that I think are making the world a better place:
Minti.com – a parenting site that people seem to really use to reach out and find solutions and fellowship in parenting.
FreeRice.com – a mindless game you can play where the more you play the more rice they donate to the World Food Program. Does it make a difference? I dunno, but I like the idea of the energy people put into games being recycled into something useful.
SchoolPulse.com – full disclosure: we made this. That being said, the idea of teachers, parents and school administrators having another way to communicate appeals to the BBS guy in me who thinks that people can open up in different and sometimes better ways through digital media.
current.tv – I actually liked the last version more than this, it was easier to find the indie political videos. I like getting my news from the many, not the few.
I'm not going to name a political site, cause it's been done to death and frankly I don't really spend any time on a candidate/issue site.. weird.
Besides, that'll give you some thing to post about, and tell me what else am I spacing?
If the web can make the world a better place, lets have some more examples….