If you re like many investors, chances are you have a few too many dollars parked in your brokerage account. Whether it s the proceeds from a recent (or not so recent) stock sale, a chunk of cash you like to keep at the ready for future trades, or even your emergency fund, one thing s for sure: you could put it to much better use elsewhere.

Many investors began socking away cash with their brokerages after the stock market crashed in 2008, when they liquidated their stock portfolios and ran to the safety of currency. But instead of stuffing it under the mattress or depositing it in a high-yield savings account, they just kept it with their broker.

Cash held at brokerage houses is typically deposited in so-called sweep accounts. These accounts offer convenience and liquidity, with features like check-writing capabilities, a debit card and free ATM withdrawals. Some brokerages call them cash or financial management accounts, and others have even branded them savings accounts.

The problem is that the yields these accounts deliver are paltry these days. To be sure, earning some interest is better than earning none, and for investors using the account for its original purpose a short-term parking place for cash they plan to invest a few extra dollars can feel like an unexpected bonus. But recently, many investors have begun using these parking spots as savings or checking accounts, losing out on more favorable interest rates elsewhere.

There are no hard numbers on the amount of cash lying around in sweep accounts these days, and chances are that with the stock market s recovery from its 2009 lows and the Federal Reserve s rock-bottom rate policy, some investors are moving it into equities or higher-yielding bank accounts. Still, the assets parked in sweep accounts could add up to $600 billion, according to Peter Crane, president of Crane Data LLC, which tracks money-market mutual funds.

That s not necessarily the most lucrative place for all that cash from an investor s perspective, at least. For every $10,000 you keep in a brokerage account, you could be earning an additional $150 a year by simply moving them to a high-yield savings account at a bank.

Here s why. These days, sweep accounts pay an average 0.05%, according to Crane Data, but depending on the brokerage, you could be earning as little as 0.01% and rarely more than 0.07%. (For specific yields, see our table below.)

Even that was considered paltry In December 2007, with the Fed funds rate at 4.25%, sweep accounts yielded an average 3.1%.

For the most recent development in these fee wars, read our story Online Trading Price War Heats Up

Richard Bove, a banking analyst with Rochdale Securities, says that given the probability of higher-capital requirements on the part of the brokerage industry and the fact that they re going to have to pay a tax on their net liabilities, brokerages simply aren t interested in attracting deposits and therefore have no incentive to boost their yields.

Ken Bergeson, a product manager for Wells Fargo WellsTrade, says that the bank s yields are competitive and adjusted periodically. The bank s sweep account currently pays 0.03% a year on household balances up to $499,999 and as much as 0.20% for Wells Fargo Private Bank clients who have assets of more than $1 million.

Still, investors could be doing better if they simply chose to link their brokerage account to another Wells Fargo account. (They could continue to make fee-free and immediate transfers when the cash is needed for trades.) One such option is the Prime Checking Account where they can earn anywhere from 0.05% (on balances up to $4,999) to 0.40% (on balances of $100,000 or more).

You could do even better if you parked your cash in a high-yield savings account at an external bank, which these days could pay as much as 1.55%. The caveat? These yields are typically offered by banks that don t have a large branch network (or have no branches at all), and cash transfers between the bank and your brokerage could take several days. That s because the best yields these days are offered by banks that are trying to grow their deposit base, and those are typically smaller or online banks that don t have many branches. It s a whole lot cheaper to offer 1.5% on a money-market deposit account than to try to compete toe to toe with the marketing budget of a mega bank, and it s cheaper than going out and building scores of branches with the goal of growing deposits, says Greg McBride, a senior financial analyst at Bankrate.com.

E*Trade, for example, holds transfers from external accounts for three business days before making the funds available for investment or withdrawal, according to a company spokeswoman. In the worst-case scenario, a several-day delay could cost you an opportunity to buy at a rock-bottom price, Crane says.

At the end of the day, where you put your cash should depend on what you plan to do with it. A high-yield savings account is not suitable for money that you would want to put back into the market on a moment s notice, says McBride. But it is very well suited for your rainy day fund or money you just want to put aside for a while.