Seeing as how School is coming back up soon for many of us, and unfortunetly some posts and Bios can be hard to read at times, I figured these links might help. Obviously the best way to get better is to practice as these aren't always accurate, but they do help and make your posts and bios much easier to read.
http://orangoo.com/spellcheck/ -> Copy and paste or type in your text. It also has a translator, Dctionary, and a grammar checker all in it as well.
http://www.spellcheck.net/ -> This one's really simple but works well. Just drop your text in and go.
www.grammarcheck.com/archives/searching.htm -> This one has you type in a word and then it directs you to a search containg several diffrent uses of the word
Microsoft Word and Firefox if you have either also have Spell checkers built in. I haven't used Firefox in a while so I don't know if it has a grammar checker but Word defiantly does. Any other resources that people want to add to this, post and I'll add it.