Common grammar/spelling errors that are easily avoided

JCSoRocks dropped me a friendly note on the forums, and I saw his signature contained the following:

loose != lose

There are a number of easily avoided English screwups.

1. Rediculous -> ridiculous
2. Irregardless -> regardless (irregardless is a double negative, so literally negates its meaning)
3. Their/they're/there = They're (they are) busy putting their (ownership) brains over there (place).
4. Whose/who's = Who's on base, and whose jockstrap is that in the corner?
5. It's/its = It's (it is) a good day for any weird creature to enact its (possessive) revenge upon Tokyo.
6. And of course: Don't lose your loose change.

Any others?