Virtual Stock Exchange

You can practice investing in the stock market for free, and see how you would do.  The site is also planning to offer access to pay-to-play competitions where you can win money.  Found by Jean Jasmine O. Sevilla.

MaxFunds

Helps you choose mutual funds.

Bankrate.com

This page will help you find the best interest rate for a credit card, auto loan, or mortgage.  There are also different financial calculators.  For example, you can calculate payments on an auto loan, calculate payments to get rid of credit card debt, find the cost of raising a child, or figure out how long it will take you to become a millionaire.  Found by Krysia Salagaj.

X-rates

Use the currency calculator on the left-hand side of the page to convert one country's money to another.  Found by Jackeline Gonzalez.

Fuel Economy

Find the cheapest gas in L.A. (or anywhere else in the U.S.) Also, you can compare miles per gallon for different cars.  Found by Aram Khachoyan. 

Investing On Line

Some basic information about investing online.