There's an interest-rate war going on, and with a little detecting, you can garner the spoils. Internet-based banks, battling for a share of the market, are offering enticing interest rates--5 percent and higher--on certificates of deposit, money-market accounts, and even plain old savings. These rates are typically much higher than what you could get at a walk-in branch. At the same time Citibank was paying an annual percentage yield, or APY, of 5 percent for online savings, its regular branches paid 0.7 percent a year for passbook savings.

Think of these accounts as interest generators and not much else. Most don't offer online bill payment. While many offer ATM cards, those cards usually won't double as debit cards. And check-writing is limited. Typically, you have to link your new account to an existing or new checking account. But the two accounts can provide a powerful combination of high rates and convenience.

Before you shop for an online account, take a moment to think about your plans for your money. A CD is a good place to stash cash earmarked for something specific--perhaps a home-remodeling project or next year's tuition--that you'll need around a certain time. If you withdraw the money early, you'll pay a penalty that is fixed by the bank.

Because CDs often pay higher rates than savings accounts, they obligate you to tie up your money for a fixed term, say, six months, and usually require a deposit of at least $500. According to Bankrate.com, a Web site that provides daily updates on rates from 4,800 financial institutions, the average six-month CD was paying 4.68 percent a year and one-year CDs nearly 5 percent in early October. Several Internet banks were paying 5.25 to 5.6 percent yields on one-year CDs with a minimum deposit of $500 to $1,000.

Bank money-market and savings accounts offer more flexibility but lower, floating yields. In early October they were paying 1.35 to 1.5 percent less per year than one-year CDs on average. A handful require no minimum deposit to avoid fees. They're good parking spots for emergency funds. You can also have your paychecks or Social Security checks deposited directly into money-market accounts. Some offer limited check writing, typically three checks a month. (Don't confuse bank money-market accounts with money-market mutual funds. The latter are sold by brokerages and fund companies, and are not FDIC insured.) Online savings accounts are similar to money-market accounts. In early October, the highest online annual savings yields were around 5.30 percent.

Bankrate.com is a good place to start shopping for an online account. The site's search engine can sort among banks based on their interest rates and minimum required deposits without additional fees and other variables. Go there once a week for a few weeks to scout out the most competitive institutions.

Check, too, with affinity groups. Some offer high-yielding accounts to their members. Teachers, administrators, and other professionals who belong to the National Education Association, for example, can put money into the NEA's FDIC-insured money-market accounts, which were recently yielding 5.08 percent for a $500 deposit, well above the national average of 3.46 percent.

To make the most of an online savings or money-market account, you'll need to link it to an existing checking account. You can then make periodic electronic transfers between the two. Review your checking account rules to ensure that shifting funds to savings won't saddle you with low-balance penalties. (Until Dec. 31, Citibank Direct is offering new customers a high-yield e-savings account linked to a no-fee, no-minimum-balance checking account; you need the promotional code posted on its Web site.)

To get started, you make a first deposit through the mail or electronically. Expect to wait up to 15 business days for funds from your initial deposit to become available. Your new bank may make a couple of trial deposits from your new account into your checking account to make sure the system works.

After that, you can begin transferring money to and from the new account. By law, you can make only six transfers per month from your online money-market or savings account into your linked checking account. The online banks don't limit transfers in the other direction. Check with the bank that hosts your checking account, however, for any restrictions it may impose.

Here are other features to consider:

Interest rates. The operative term in these accounts is annual percentage yield, the interest you'll earn. That yield may sometimes include a higher introductory rate, so make sure you know what the regular rate will be before signing up.

Fees. Monthly service fees for money-market and savings accounts can be as high as an eye-popping $25 a month at online banks. You may be able to avoid fees by maintaining a minimum balance.

Check-writing privileges. Money-market accounts offering them allow just three a month per account.

Direct deposit. Usually, you can have paychecks and Social Security checks deposited into online banks electronically.

Extras. Capital One, Citibank, and HSBC Direct offer free ATM cards that draw directly from your new account. You can use them as often as you like.

With such competitive interest rates, online savings accounts are a good option for anyone with Internet access and a checking account. Because the setup is fairly straightforward, even folks who nearly empty their accounts every month might find those extra pennies in interest worth the effort.