1. When people say "a whole nother". I hear this one a LOT. What's a "nother" anyway, people? The proper way to say this phrase is "another whole."
2. Mixing up to/too/two. I don't usually see the number (two) get mixed up as much as the others do. "Too" means also. "To" doesn't.
3. Mixing up there/their/ they're. "There" refers to location, as in to go over there. "Their" is possessive, as in their house or their car. "They're" is a contraction of they and are. For example, they're going on vacation.
4. Improper use of apostrophes. This is probably my number one pet peeve. I can't stand it that people throw in an apostrophe any time a word ends in the letter "s". I was visiting my parents' ward yesterday, and there was a basket in the mothers' room that said, "Mom's Helping Mom's." ??? That translates to "Mom is Helping Mom is." See how little sense that makes? An apostrophe should be used to show possession, as in "Mom's shirt," indicating that shirt belongs to mom. It should also be used for contractions when the word "is" is being included with another word. Example: "Mom's silly." An apostrophe should NOT be used anytime a word ends in the letter "s". Please. Don't.
And that's all for my venting today. Please feel free to correct my grammar anytime. I welcome it!!