HF verticals are a popular antenna option when trees and towers aren’t available.  They are the antennas of choice on the low bands for working DX, as most hams can’t get horizontal antennas high enough to be as effective as a vertical on 80M.  They can be surprisingly effective with a good radial or ground system, and disappointing over poor ground.

• The "C Pole"— A Ground Independent Vertical Antenna
  QST April 2004, pp. 37-39
  KF2YN takes the vertical to new heights with this folded design that doesn’t require a counterpoise.
• A Ground-Coupled Portable Antenna 
  QST January 2001, pp. 28-32
  A 10 foot vertical antenna that works from 40- to 6 meters. .
• The Ground-Image Vertical Antenna
  QST July 1971, pp. 16-19, 22
  Theoretical considerations and experimental results on a vertical antennas.
• A Four-band "Tree" Vertical 
  QST November 1995, pp. 69-70
  If the thought of a high-visibility HF antenna leaves you cold, it's time to branch out and get to the root of the problem...
• A Modest 45-Foot DX Vertical for 160, 80, 40, and 30 Meters 
  QST September 1981, pp. 27-31. Feedback QST November 1981, p. 50
• The Offset Multiband Trapless Antenna (OMTA)
  QST October 1995, pp. 30-32.
  Feedback QST December 1995, p. 79
  Simple, easy to build, low cost, compact, multiband ... interested?
• Designing a Vertical Antenna 
  QST September 1978, pp. 19-21
  Graphs cut through the mathematical headaches of antenna design.
• Efficient Ground System for Vertical Antennas 
  QST February 1983, pp. 20-25
  Elevated ground systems for vertical antennas have been a bit of a mystery for the past 60 years. This report of an extensive study reveals some startling results.
• A Two-Element Vertical Parasitic Array for 75 Meters 
  QST December 1995, pp. 38-41
  What do a city lot, $50, about half the wire in a dipole, old coax and 6 db of gain have in common?
• Build a Lightweight 20-Meter Vertical 
  QST December 1995, pp. 64-67
  Could this be the lightest HF vertical in the world?
• Simple 5/8-Wave Vertical for 12 and 17 Meters 
  QST April 1989, pp. 19-20
  Here's how to turn a 30-meter quarter-wave vertical into a 5/8-wave radiator for the 12-meter band. And there’s a bonus: you can use the same approach to use your quarter-wave 40-meter vertical as a 5/8-wave antenna on 17 meters!
• An Efficient Multiband Vertical for 160 through 20 Meters 
  QST October 1998, pp. 45-49
• A Disguised Flagpole Antenna 
  QST May 1993, p. 65
• A Simple and Portable HF Vertical Travel Antenna 
  QST July 2002, pp. 28-31
  How to build a portable, efficient 40 through 10-meter vertical antenna on the cheap.
  Feedback: QST August 2002, p. 58 (included in PDF file above)

Rudy Severns N6LF has written a series of articles in QEX on measurements he has done on ground systems for vertical antennas.  You can download the articles from his blog, Antennas By N6LF