The Volkswagen Type 3 Fastback was sold from 1961 through 1973 in three distinct configurations, the notchback (looks coupish), the squareback (a wagon thing), and the fastback...which is what we have here today. Power comes from Volkswagen's 1600 cc version of the aircooled flat-4 that was fuel injected starting in 1968. Find this 1969 Volkswagen Type 3 Fastback offered for $6,500 in La Habra, CA via craigslist. Tip from Rock On!
This next car comes as a tip from Jeff who writes: Wheels are lame on this one, but great miles at only 74k. Not bad for a German sedan with a V8 and a sharp lookin' ride for $10k. The W219 generation CLS-Class was built on the W211 E-Class chassis, but it was shaped like a fastback to reduce rear seat headroom. Find this 2006 Mercedes-Benz CLS500 offered for $10.975 in South River, NJ via cargurus.com.
Mustang snobs tend to gravitate towards the early 1964-65-66 or 1967-68 Fastback versions for various reasons that escape me at the moment (but are probably rarity, exclusivity, coolness, in that order) but random yokels on the street know one thing about a classic 60s Mustang. The 69 Mach 1 was the coolest. Find this 1969 Ford Mustang Mach 1 offered for $20,000 in Jacksonville, FL via craigslist. Tip from FuelTruck.
I'm as skeptical as the next guy about sellers claims of rarity, but I have to admit that I don't think I've seen a Volkswagen 411 on the road in the past decade or so. Rare when new and rare today are two totally different things, but this next car is certainly something you don't see driving around much nowadays. Perhaps there is a good reason for it...but that shouldn't stop you from buying one of the 367,000 examples that left the factory between 1968 and 1974. Find this 1972 Volkswagen 411 here on eBay bidding for $2,300 with 2 days to go, located in McConnelsville, OH.
If you take a 69 Fastback Volkswagen and drop a larger engine inside...no one will argue that the car still isn't a Type 3. Even if that engine is a flat-6 or a V8, as long as it lives in the rear and still uses some of the bodywork, no one will argue with you. But, what if you replace the frame, engine transmission and every moving part with an assortment of welded Chevy parts...is it a Volkswagen anymore? Find this 1969 Volkswagen Fastback offered for $12,500 in Olympia, WA via craigslist. Tip from Rock On!
I can't tell you exactly what this next thing started life as, but I can tell you that it it isn't a Mustang Fastback, in kit form or otherwise. The ONLY thing it shares with the Mustang Fastback ('67, '72 or otherwise) is that it has 4-wheels and a fastback style rear glass window (but Ford didn't pull their window from a scrap pile out behind the nearest Home Depot.) Find this not a 1967 Ford Mustang Fastback 3/4 Kit offered for $2,500 CAD ($1885 USD at time of publication) in Toronto, ON via kijiji.ca. Tip from John.
A picture is said to be worth a thousand words. Truer words have never been spoke with this matching numbers fastback Mustang c-code 302 V8 2 barrel car that is completely in pieces. The seller warns potential buyers to be not discouraged by the scary pictures especially ones of the car shell sitting atop of two stoves. They are a little negotiable on price and delivery is possible. Find this 1969 Ford Mustang Fastback for sale in Smithtown, NY for $3,500 via craigslist. 
The MGB GT was a 2+2 fastback version of MG's entertaining 2-seat MGB roadster, and with today's classic car market they offer a decent package for a low entry price. This next one has had over $12k in repairs/restoration in the past 4,000 miles... and remember, there is no money better spent on a car than the previous guy's. Find this 1973 MGB GT offered for $7,000 in Santa Fe, NM via craigslist. Tip from FuelTruck.
Check out this 1968 Ford Fairlane 500 Fastback here on eBay bidding for $7,100 with auction ending on Monday at 5:30PM.
Take a look at this 1970 Ford Mustang Fastback here on eBay bidding for $20,100 with auction ending Thursday around 3PM PST.
The 1969-1970 Ford Mustang fastback is one of the better looking cars to ever leave a factory in Detroit, and I'm not just saying that because I've got one in the garage. Actually they didn't just leave factories in Detroit, because at the height of Mustang madness they left assembly plants in Dearborn, San Jose, New Jersey, Mexico City, and Venezuela. Regardless, the '69 Sportsroof as designed by the guys under Gale Haldeman is something special. Find this 1970 Ford Mustang Mach 1 here on eBay
bidding for $13,000 with 2 days to go, located in Erlanger, KY.
Somewhere between the cute 'n' tiny Honda S500 and the later (and more common) Honda S800 lives the Honda S600. It was the first of Honda's S-cars to get a hardtop version, but still featured a roller bearing 600 cc 4-banger and a chain driven rear end. Find this 1965 Honda S600 Fastback Coupe bidding for $5,685 reserve-not-met here on eBay and for $10,000 here on craigslist, located in Staunton, VA. Tip from seant.
DT -- This next 1973 Ford Mustang Fastback offered for $5,999 on craigslist, located in Sandown, NH comes as a tip from Scott T, who writes: 
The 3rd refresh of the original Mustang sold in '69 & '70 is one of my favorite fastbacks, not just because of the TransAm racing looks, but also because you get so much more car for your money. For the same price as this next feature you would be shopping for a rusted out '65 or one of those coupes converted to fastback. Find this 1970 Ford Mustang Fastback here on eBay
currently bidding for $9,100 located in Honolulu, HI.
Does anybody remember that ulta-realistic third installment of the Fast and Furious series where high school kids (poor Texans and Yakuza members alike) drive 500 horsepower drift machines with easily $100k in aftermarket parts? Between the RX-7s, Evos, Zs, and Tourans you might have missed the star of the movie, an RB26DETT swapped 1967 Ford Mustang fastback, except that isn't this car. The Japanese inline-6 powered fastback was used for some static shots, but the real star of the climatic drift scene was a 403 cubic inch V8 powered beast that was bashed up on screen -- that's what we've got here today.
Listen up kids. You should study in school. You need to stop huffing glue and start hitting the text books. Because those grades will make a difference as to which school you go to and later how big your paycheck is...because it isn't too late. Sure, you'll never be able to afford a C2 Corvette, E30 M3, or anything with the Shelby name (that isn't a Dodge)...but...you can still pick up a '69 Fastback for a reasonable price. For the next 5 minutes at least. Find this 1969 Ford Mustang Fastback here on eBay
currently bidding for $15,300 with 4 days to go, located in Anaheim, CA.
In 1969 the Ford Mustang received its 2rd major restyle in 3 years, but this design lasted only a year before it was given another facelift. The 1970 facelift was only a minor change to the front fascia, but the rear 1/4 panels were reworked to remove the faux side scoops. The amount of money Ford spent each year retooling their entire lineup back in the day might not be matched by today's exorbitant salaries bestowed on their CEO, but it's gotta come close. Find this 1970 Ford Mustang Fastback offered here on eBay
in Islip, NY currently bidding for $4,150 with 1 day to go.