If you're looking for some great math practice problems, Twitter can be one place to turn. It's also convenient since you're probably logging in to tweet on a regular basis anyway. Here are some "Tweeters" to consider if you're looking for some extra practice or a challenge.
Description: The National Council of Teachers of Mathematics tweets primarily high school level problems. Questions go out in the morning, answers at night.
Example Problem: How many different rectangles can be drawn using the hour marks on a clock's face as vertices?
Frequency: Problems tweeted every weekday.
Description: Mainly high school level questions are posed. Students posting answers get props via Mathprobs twitter feed or are encouraged to try again.
Example Problem: 1101011010110 in base 2 = what in base 4???
Frequency: About once a week
Description: Tweets here are for middle through high school students a little less frequently than some of the others.
Example Problem: How can you add eight 8's to get the number 1,000?
Frequency: About once a month
Description: Provides a link to an SAT question of the day. These questions are a mix of math and verbal.
Example Problem: A train travelling 60 miles per hour for 1 hour covers the same distance as a train traveling 30 miles per hour for how many hours?
Description: Tweets links and a short description of questions being posed by students from algebra.com. Requires free registration on algebra.com.
Example: A lamp is marked with a sale price of $23.80, which is 15% off the regular price. What is the regular price?
Frequency: Multiple times a day
Description: Posts are questions being posted by students on a math forum. Tends to be middle school to early high school level.
Example: How many diagonals does a square have?
Frequency: About once a day
Know another great place for math problems on Twitter? Post it in the comments below.