What: A good place to start if you're concerned about whether your charitable donations are reaching those who need them.
The best parts: Site assigns a zero to four-star rating to more than 1,100 charities, based on their effectiveness and financial health. Learn how much money a charity spends to raise $1, and the percentage of revenue it devotes to fundraising, administration, and program expenses.
You can also evaluate a nonprofit's long-term sustainability based on the historical growth of its revenues and expenses. That can come in handy. Several charities not related to last year's Sept. 11 tragedy had to close their doors because of a lack of funds.
Charity Navigator also lists salary information of the person most responsible for carrying out a nonprofit's mission, and compares nonprofits with others involved in similar causes.
What you should know: The site is free to use and bases its data on the 990 forms that nonprofits file with the IRS each year. It aims to add 50 new evaluations each month, with a goal of eventually rating 5,000 nonprofits.