I see this a lot in blogland, so I wanted to provide a quick "lesson" along with the trick I use to choose the proper pronoun.
Many people use pronouns incorrectly, especially when using "I" with another pronoun. Here's the rule... take the other party out of the sentence, and figure out which pronoun you would use. For example, "Me and Matt are going to the store." Take out the "and Matt." You wouldn't say, "Me is going the store." You would say, "I am going to the store." So, the proper grammar would be, "Matt and I are going to the store." You always put yourself last. Conversely, "This is a picture of Matt and I," or in captioning a picture, "Matt and I." You would not say, "This is a picture of I." You would say, "This is a picture of me." I'm not going to pretend like I don't trip up sometimes and use "I" when it should be "me," but this is the trick I use when I'm unsure. I think a lot of people use "I" in place of "me" even when "me" is the proper pronoun, because "I" tends to sound more intelligent. So, if you're guilty of this, remember this little rule, and you'll get it right!
This message brought to you by Grammarians Anonymous, a support group for people who know, or think they know, too many rules of grammar.