If you're in the market for a new car and have an old clunker to trade in, you'd better act this weekend. The federal government has announced that its popular "Cash for Clunkers" rebate program will end this Monday, Aug. 24 at 8 pm.

The program was originally intended to run through November 1. However it nearly ran out of funds just in its first week of operation. While the federal government allocated $2 billion in additional funding, car shoppers have nearly exhausted them. "As of [August 19], dealers had submitted 435,102 clunker transactions to the Transportation Department and requested $1.8 billion in reimbursements," reports the Los Angeles Times.

Though largely a success, "Cash for Clunkers" has also been controversial. Initially, buyers and dealers complained that the demand for some vehicles outnumbered dealer supplies. More recently, dealers have complained that they're yet to be reimbursed for many of the rebates they've given under the program. The National Automobile Dealers Association (NADA) has even begun warning its members against taking "clunker" trade-ins for fear of not being reimbursed. Nevertheless, the program continues through this weekend.

To take advantage of Cash for Clunkers before it's too late, educate yourself on the program's details with U.S. News' Cash for Clunkers page. Read on for the skinny on five of the most popular vehicles acquired through the program.

Toyota Corolla

MSRP: $15,350 - $20,050
MPG:
26 City / 35 Hwy

The Toyota Corolla is comfortable, fuel-efficient and reliable -- perfect for everyday commuting. Some class competitors offer funkier styling and sportier handling dynamics, but the Corolla doesn't need to rely on gimmicks. Free of fuss, it delivers the essentials like few others can. In fact, U.S. News named the Corolla a top pick among compacts for its 2009 Best Cars for the Money award.

More Savings: If you live in the Gulf States, Toyota will give you an extra $1,000 cash back when you buy a 2010 Corolla by 08/30/09. For more discounts and incentives, check out U.S. News' Toyota Deals page.

Ford Focus

MSRP: $15,520 - $18,265
MPG:
24 City / 35 Hwy

Not only is the Ford Focus a competent performer, but it offers generous cargo room and some really cool standard and optional features -- including an easy-to-use SYNC infotainment system. Even better, it won't hurt your wallet at the pump. Still, buyers should note some drawbacks, including a cramped backseat and bland exterior design.

More Savings: Receive an additional $1,500 Retail Bonus Customer Cash plus $500 to $1,000 Retail Customer Cash (depending on trim) if you buy a 2009 Focus before 8/31/09. For more discounts and incentives, check out U.S. News' Ford deals page.

Hyundai Elantra

Starting MSRP: $14,120 - $17,820
MPG:
24 City / 33 Hwy

Bargain hunters take note, the Hyundai Elantra has a little bit of everything -- class-competitive fuel-economy, comfortable seats, loads of convenience gadgets, useful cargo space and one heck of a warranty. Though the Elantra doesn't stand out for its design or performance abilities, most critics agree that it's good on both fronts. It's even a U.S. News 2009 Best Cars for the Money award winner.

More Savings: If you buy a 2009 Elantra before 8/31/09, you'll be eligible for an additional $1,500 to $2,000 rebate (depending on trim).

Chevrolet Cobalt

MSRP: $15,660 - $23,525
MPG:
25 City / 37 Hwy

Too small for families, but just right for teens and young adults, the Chevy Cobalt is easy on gas, comfortable on the road and offers loads of awesome entertainment options -- including Satellite Radio and a seven-speaker Pioneer sound system. Reviewers complain of tight quarters in the rear, but find its one-year of complimentary OnStar service a major plus.

More Savings: Lock in zero percent APR for 60 months if you finance a 2009 Cobalt by 8/31/09. For more discounts and incentives, check out U.S. News' Chevy Deals page.

Honda Fit

MSRP: $14,750 - $18,960
MPG:
27 City / 33 Hwy

Unlike the Cobalt, the Honda Fit's spacious interior and class-leading cargo options make it perfect for singles and small families on the go. What's more, it boasts fuel-efficient, fun-to-drive handling dynamics and a modern, quirky design. And though the base trim lacks stability control, it's still an insurance industry "Top Safety Pick." Altogether, auto critics love the Fit. Its numerous awards include U.S. News' 2009 Best Small Car for the Money.

More Savings: Honda isn't offering any additional discounts or incentives on the 2009 Honda Fit this month. However, if you're eligible for a $4,500 CARS discount, you can buy a Fit for low as what you'd pay for the regularly-priced Nissan Versa.