80/75 Meter 4-Square Array by K7EM
This array has been in use since 1989. The SWR from 3.5 to 3.9 is below 1.5:1. The F/R of the array is 20dB average and with some signals even better.
http://www.bctonline.com/~skelly/4square/4square.html

80 Meter Frame Antenna by SMØVPO
I keep on and on about my little balcony and the antenna restrictions it imposes on my HF antennas. This project was developed as a result of experiments to become QRV on 80 meters, again, using the little balcony.
http://www.sm0vpo.com/antennas/frameant.htm

80m Short Dipole by 4S7NR
I have nothing much to write. Every one of us can't have a full size 80m dipole (even me). This is not good as a full size one, but it is much better than no antenna. HI!
http://www.qsl.net/qrp/ant/short80.htm

A Short Dipole for 80m by 4S7NR
The antenna above has been described by Nadisha, 4S7NR and may be of interest to anyone wishing to get on 80M (3.5MHz) that have limited space available. L1 is 12 feet. L2 also is 12 feet and the overall length is 48 feet.
http://www.zerobeat.net/g3ycc/4s7nr.html

Coax Dipole by N4SEV
Here are some simple antennas you can build along with calculators to help you get the right length.
http://www.n4sev.net/joesantennafarm/
 

An End Fed Halfwave Antenna by G3YCC
This end fed type of antenna was marketted in the UK and is a useful system for the portable set-up. Being a half wave, no radials or counterpose wires are needed.
http://www.zerobeat.net/g3ycc/endfed.htm

The End-Fed Halfwave Antenna by AA5TB
The end-fed halfwave antenna is among my favorite for field operation. It is easy to setup, can be used without a feedline, and performs well. The end-fed halfwave antenna is a resonant half wavelength long antenna ...
http://www.aa5tb.com/efha.html

Goedkoop op 80/40 (en 20/10 meter met tuner) zelfbouwdraadantenne door PA3HMP
Vanwege de vele positieve recties heb ik maar wat haast achter het tweede artikel gezet, dit ter meer omdat je beide draadantennes kan combineren en je dus een draadantenne kan maken met in iedere poot twee traps, ...
http://www.pa3hmp.nl/draadant-2.htm

My slopers for 80 and 160 Mt by IK4DCS
As for all long-wire antennas also these that I am going to describe arevery simple but incredibly efficient. I actually discovered this type of antenna owing to some problems with available space around my house.
http://www.qsl.net/ik4dcs/slopeng.html

The NJQRP Squirt by N2CX
This reduced-size 80-meter antenna is designed for small building lots and portable use. It’s a fine companion for the Warbler PSK31 transceiver.
http://www.arrl.org/tis/info/pdf/0104040.pdf

Top Fed Linear Loaded 3/4 wave length Vertical for 80 meters by KE4UYP
This is a vertically polarized Phased array. The left Vertical wire is 180 degrees out of phase with the middle and right Vertical wire. At 1/10 wavelength spacing from the right Vertical wire to the left Vertical wire it is producing a End-Fire Bidirectional Pattern,that developes a Gain of 5.9-DBi.
http://ke4uyp.tripod.com/80m_Antenna.html