A $20 HF Mobile Antenna by KM4IE
A few hours of fun with PVC and wire and you’ve got yourself a respectable road radiator!
http://www.arrl.org/tis/info/pdf/0004033.pdf
 

A High Efficiency Extended Length Mobile Antenna by W5JGV
Much taller than the average Ham mobile antenna, this tree branch snapper tops out at 17 feet, 10 inches above the road. The antenna itself is 3.42 meters or 11 feet 2 inches long from the top of the mounting spring to the tip.
http://w5jgv.com/mobile_antenna/index.htm

A Linear Loaded Vertical Antenna for 40m and 80m by PA3HBB
As a lot of you will appreciate, to work good DX requires a low angle of radiation from the antenna. It is possible to achieve this low angle with a horizontal antenna, but only if sufficient height above ground can be achieved.
http://www.qsl.net/pa3hbb/ll.htm

Balcony Antenna by SMØVPO
Many amateurs are very restricted with the space they have available for HF antennas. I have documented a short antenna for the HF bands, but here is a simple method of mounting it, and a method of further reducing the length.
http://www.sm0vpo.com/antennas/balcant1.htm

Balcony Antenna Extension by SMØVPO
You may have already seen my HF Balcony Antenna which was designed solely for 14MHz, then a coil was added to cover all the lower HF bands (10, 7 and 3.5MHz).
http://www.sm0vpo.com/antennas/balcant2.htm

Build the PAC-12 Antenna a multi-band portable vertical designed by KA5DVS
Here’s an award-winning, easy-to-homebrew, multi-band portable vertical antenna designed by long-time antenna aficionado James Bennett, KA5DVS. He’s documented the design and construction plans for a portable antenna...
http://www.njqrp.org/pac-12/

Build This Novice Four-Band Vertical by WB1FSB
Putting your first amateur station together can be an expensive proposition. One way to cut costs is to keep the antenna simple. Here's how I shaved the price and provided four-band operation.
http://www.arrl.org/tis/info/pdf/7806016.pdf

De "SCREWDRIVER" Antenne door PHØRMH
Nevenstaande antenne, de “screwdriver” antenne wekte mijn belangstelling op de Hamvention 2000 in Dayton. Op verschillende, voor zendfanaten interessante stands, stond het ontwerp van Don Johnson W6AAQ.
http://www.pi4asv.nl/techniek/antennes/screwdriver.html

Effective HF-antenna for mobile operation by OE3MZC
Mobile operation on HF bands requires high efficiency antenna systems with a very rugged design and slim profile for low wind resistance. The following description should give you guidance on how to build a mobile antenna for HF bands yourself, using a very cheap CB-mobile whip antenna base.
http://www.qsl.net/oe3ycb/mobileantenna.html

IC706/FT817 portabele "whip" antenne door PAØFBK
Een ander leuk antennetje is zeer geschikt voor bezitters van bv. een IC706 of FT817, maar natuurlijk werkt het ook met andere transceivers en ontvangers. Met deze antenne kun je overal binnen een paar minuten qrv zijn, ...
http://www.qsl.net/pa0fbk/hampage_nl.htm#whip

Mobile/Portable HF Whip by G3YCC
I thought it may be of interest to describe simple to make HF whip antennas I have experimented with and used for a while.
http://www.zerobeat.net/g3ycc/yccwhip.htm
 

Multiband Vertical Antenna Project by KV5R
The purpose of this project is to design a simple multiband vertical dipole antenna for 20 meters and above, with a tuner, that will provide gain and a circular pattern on the higher bands.
http://www.athensarc.org/KV5R%20Vertical%20Antenna%20Project.doc

The Offset Multiband Trapless Antenna (OMTA) by AL7KK
Once in a while an idea turns out to be so good that it can’t stay a secret. The offset multiband trapless antenna (OMTA) is so simple to build, so easy to employ and works so well, it fits that category.
http://www.arrl.org/tis/info/pdf/9510032.pdf

Short Antenna by SMØVPO
"QRP" operation often means operating in remote places where a decent full-sized antenna is not possible. I personally live in an appartment where I am unable to erect large antennas.
http://www.sm0vpo.com/antennas/short.htm

St. Louis Vertical by NFØR
The St. Louis Vertical (SLV) offers portable enthusiasts an easy-to-build, easy-to-use antenna which covers 10-40M via a balanced line tuner.
http://www.amqrp.org/projects/stluisvert/STLV%20Project.html

The FARAPole, a portable antenna for 6 through 20m by WA1GPO
The FARAPole project was designed and developed by FARA member Jim Valdes, WA1GPO as an adjunct to the Yaesu FT-817 HF transceiver.
http://www.falara.org/tektalk/farapole.html