"You absolutely have to be buying oil stocks into this weakness," said James Cramer Wednesday on his

"RealMoney" radio show.

Last week, Cramer said he saw mutual funds buying oil stocks into the end of the quarter to show the stocks on their books at quarter-end. This week, Cramer sees mutual funds selling oil stocks to lock in gains. But, he said, the earnings of smaller oil companies and integrated oil companies -- ones that also make plastic and chemicals -- are "only just beginning to be great."

Examples of companies Cramer would be buying into weakness include

Valero Energy

(VLO) - Get Report

, which he would look to buy around $100,

Halliburton

(HAL) - Get Report

,

Schlumberger

(SLB) - Get Report

,

Occidental Petroleum

(OXY) - Get Report

and

EnCana

(ECA) - Get Report

.

Cramer would avoid "big oil" stocks such as

BP

(BP) - Get Report

,

Royal Dutch Petroleum

( RD),

Exxon Mobil

(XOM) - Get Report

and

Chevron

(CVX) - Get Report

.

Whereas the weakness in oil stocks is a buying opportunity, the weakness in homebuilders' stocks is not. The homebuilders "are finished," said Cramer. Homebuilders' stocks can't seem to get out of their own way, he said.

Cramer believes the weakness in homebuilding stocks is signaling weaker earnings ahead for the companies even though they have yet to experience a slowdown. With the

Federal Reserve

continuing to raise interest rates, though, and despite generally excellent management, Cramer believes the homebuilders' businesses will go south before too long.

"I don't like the homebuilders anymore," said Cramer. You should sell the stocks on any rally or even if they don't rally, said Cramer.

Picks and Pans

In his weekly "Am I Diversified?" segment, Cramer said these things about stocks in listeners' portfolios:

OSI Pharmaceuticals

( OSIP): The stock is very controversial, and Cramer doesn't like the company's planned acquisition of

Eyetech Pharmaceuticals

( EYET). However, OSIP is an interesting speculation, but Cramer prefers not to speculate in biotech stocks.

UnitedHealth Group

(UNH) - Get Report

: "One of my absolute favorite health care maintenance companies."

EnCana: Cramer would buy more EnCana today if his restrictions allowed.

Newfield Exploration

(NFX)

: "One of the finest oil and gas companies out there."

E*Trade Financial

(ET) - Get Report

: A "very fine online broker."

Microsoft

(MSFT) - Get Report

: "Terrific." With the upcoming launch of the Xbox 360 and later the new Longhorn PC operating system, it's a "mistake to sell the stock."

MEMC Electronic Materials

(WFR)

: The company's products, silicon wafers, are in high demand and supply is short.

ConocoPhillips

(COP) - Get Report

: One of the few major oil and gas companies Cramer likes.

Duke Energy

(DUK) - Get Report

: The stock seems stuck, but Cramer thinks it will be fine.

Yahoo!

(YHOO)

: Yahoo! is now cheaper than

Google

(GOOG) - Get Report

, said Cramer. He is bullish.

St. Joe

(JOE) - Get Report

: Cramer wants to buy when the stock breaks $60. St. Joe traded at $59.90 late Wednesday.

eBay

(EBAY) - Get Report

: Paid too much for Skype, but eBay is doing well.

Sears Holdings

(SHLD)

: Cramer believes those running Sears are so smart that "sometimes brains transcend everything."

Domino's Pizza

(DPZ) - Get Report

: Some are selling the stock thinking high gasoline prices are hurting the company. But, business remains fundamentally strong, said Cramer.

Royal Caribbean Cruises

(RCL) - Get Report

: Some are worried energy prices will hurt the cruise lines. Cramer thinks that's a mistake.

Montpelier Re Holdings

(MRH)

: It's tough to tell if the company has its arms around losses from Katrina, said Cramer. If it does, the stock is fine. If not, the stock has more downside, he said.

Finally, Cramer said he is a fan of the

(PZFVX) - Get Report

John Hancock Classic Value Fund because of its fund manager, Rich Pzena, whom Cramer has known for 20 years. "I think this is a great opportunity to get in his fund, and I would use it," said Cramer.

At the time of publication, Cramer was long EnCana, Halliburton, St. Joe, Microsoft, Occidental Petroleum, Sears Holdings, UnitedHealth Group and Yahoo!

James J. Cramer is a director and co-founder of TheStreet.com. He contributes daily market commentary for TheStreet.com's sites and serves as an adviser to the company's CEO. Outside contributing columnists for TheStreet.com and RealMoney.com, including Cramer, may, from time to time, write about stocks in which they have a position. In such cases, appropriate disclosure is made. To see his personal portfolio and find out what trades Cramer will make before he makes them, sign up for

Action Alerts PLUS. While he cannot provide personalized investment advice or recommendations, he invites you to send comments on his column by

clicking here. Listen to Cramer's RealMoney Radio show on your computer; just click

here. Watch Cramer on "Mad Money" at 6 p.m. ET weeknights on CNBC. Click

here to order Cramer's latest book, "Real Money: Sane Investing in an Insane World," click

here to get his second book, "You Got Screwed!" and click

here to order Cramer's autobiography, "Confessions of a Street Addict."