'RealMoney' Radio Recap: Take the Plunge!

"Don't just stand there, buy something," Jim Cramer told his "RealMoney" radio show listeners Tuesday, saying that this down day is the one-day sale that screams "buy."

Cramer said there have been tons of markets that have seen only one bull market at a time but this bull market has choices galore.

Semiconductors and retail; oil companies and airlines; railroads and truckers; insurers, and savings and loan institutions -- they're all rallying, he said.

And for every expensive company like Seagate(STX Quote) or Intel(INTC Quote), there's a Marvell(MRVL Quote) or a Broadcom(BRCM Quote), Cramer said.

For every Google(GOOG Quote) or Yahoo!(YHOO Quote), he said, there's a Pulte Home(PHM Quote) or Lennar(LEN Quote).

These are dichotomies that rarely happen, when we see expensive and cheap stocks -- stocks with very little going for them over the short and long term -- all working, said Cramer.

There's lots of capital on the sidelines waiting for the first dip to get in, and here it is, Cramer said, urging listeners to get in first.

A caller wanted to know if Ediets.com(DIET Quote) is a buy, given the fact that NutriSystems(NTRI Quote) has done well.

Cramer said that he'd looked at it as a breakout play but decided that the business wasn't good enough. Though its revenue is growing strong, Cramer said he believes it's reflected in the stock price.

Plus, at about $7, the stock is near its 52-week high.

On the other hand, Cramer said he would stand by Radiant Systems(RADS Quote), a company that makes integrated retail automation systems.

"The stock has done nothing since I recommended it," he said, but Cramer likes the company because it sells at 30 times earnings and is growing at 17%.

Cramer said it reminds him of Shanda Interactive(SNDA Quote) and that it's just a matter of time before Radiant goes higher.