Actually, 'alright' isn't considered wrong in all circles. It is thought to be similar to always (instead of all ways), altogether (instead of all together), and so on. Here is an interesting page talking about it: http://www.randomhouse.com/wotd/inde...?date=19990604

Some teachers/editors find it acceptable, and some say it's not. Spell checks generally flag it, but it is in the dictionary, though labeled as non-standard.

As far as common spelling errors, I suppose one that comes to mind is people spelling deity as diety. You go on a diet to lose weight, you don't worship a diety .

As far as a behavioral peeve, I suppose my biggest one is witnessing people deliberately trying to put down and hurt someone else. It really upsets me.

edit: Oh, thought of another grammar usage one. When people say "I keep itching this mosquito bite." You scratch an itch, you don't itch an itch,