Treasury bills are usually offered in maturities of 3 and 6 months, and 1 year. Now, though, there are 4-week bills, which can work to investors' advantage in a couple of ways. 

First, it gets you your money back faster than with the longer-term bills, and they also carry somewhat higher interest rates than similar investments, such as 1 month CD's at your bank. Also, income from them is not taxable at the state level. 

There are some negatives, though. 4-week T-bills aren't offered the same way longer duration bills are, such as over the phone, via mail, or on the Internet. To get one, you'll have to go to a bank or brokerage, and there'll probably be a fee. Depending on what the fee turns out to be, you might be better off with another type of investment. 

You can get a 4-week T-Bill for $1,000. Minimum investment for longer term bills is $10,000. There is information on the web at www.treasurydirect.gov (remember, you can't buy them on-line) or by phone at 1-800-722-2678. 

Jordan E. Goodman is America's Money Answers Man. He is a regular contributor to Public Radio International's The Marketplace Morning Report and  appears frequently on NBC's The Today Show, PBS, MSNBC, CNN, CNBC, and Nightline. For 18 years, Mr. Goodman was on the editorial staff of Money magazine, where he served as Wall Street correspondent, in addition to his role as weekly financial analyst on NBC News at Sunrise for 9 years. 

He is the author of Everyone's Money Book (over 200,000 copies sold) with 6 special focus editions on College, Credit, Financial Planning, Real Estate, Retirement Planning and Stocks, Bonds and Mutual Funds and the co-author of Barron's Dictionary of Finance and Investment Terms. 

His website MoneyAnswers.com is full of resources, tips and strategies you can use to build a solid financial future.