Many pictures on this site were created using Ultrafractal (free 30 day trial) with this additional plugin by David Makin. There are many parameters to play with so the best start is to take one of the existing parameter sets (linked under several pictures on this site), you just copy the text and hit ctrl-v on the fractal view window in ultrafractal. For more information, try posting a question to http://www.fractalforums.com/
Some images on this site were created using Buddhi's Mandelbulber, some are also created using Jesse's Mandelbulb3d. For depth of field you can use Trafassel's Gestaltlupe (see this info), and for fast renders you can try Rrrola's boxplorer.
If you're feeling impatient then why not explore in real time using Peter Nitsch's mandelbox explorer
Good luck, and you can always post your new pictures onto fractalforums.org!