Visual appeal is first step toward making a sale online. People have a great ability to scan a web page quickly before reading anything about a site. Its important to capitalize on this aspect by providing a great visual stimulus. e-Book cover art has come a long way in past 5 years. High density graphics can really make your product stand out, labeling it with a high degree of professionalism and credibility.
Throughout course of my research into best design tools I have uncovered that saying "you get what you pay for" holds all too true with cover design. Here is a review of my results. It is broken down into two categories: (1)software, and; (2) design services.
If you perform a search on Google of e-book covers there really is only a few software products that dominate first few pages of results.
(1) eCover Generator by Armand Morin The cost, $97, is about price of some personally designed single covers. It is first major player is eCover software. You can create 2d and 3d book and software boxes, and recent upgrades enable you to create cd and spiral notebook covers as well. No other software needed to use eCover Generator. Armand is giving away 6 other e-books with purchase. Very professional looking samples created with this software. Windows 95/98/2000/ME/XP compatible. http://www.ecovergenerator.com
(2) eBook Cover Central This is actually a mix between templates and design service, not software. They will design your cover starting at $39.95. This is not a bad price considering some charge upwards of $100. You also receive three different images sizes of your design. Template packages start at $9.95 for 25 pre-made templates. You only need to insert your text and any other pictures that you wish to have on cover. For $49.95 you can purchase a lifetime Gallery membership, entitling you to over 540 images and templates. http://www.ebookcovercentral.com
(3) Cover Software Pro This software, priced at $97, is actually a plugin for Adobe Photoshop. So, you need to have it (~$200) in order to use software to create your cover. It also comes with a 40 minute instructional video on using software to design not only covers but entire web sites. The samples displayed at site look quite nice. Apart from having to purchase Photoshop, this appears to be a good deal. http://www.coversoftware.com
(4) Online Web Creations offering free covers without text. All images are fixed. There is a link through their site to a utility for adding text. Fairly limited but it is free. These are not highest quality images, but I suppose you get what you pay for! http://www.onlinewebcreations.com/ebooks.html
There are more companies offering services to design and produce a one time cover than there are software products. I cannot tell one from other. All appear to produce quality products. I also am not sure what they use as graphical software, but I imagine it is something along lines of Adobe Photoshop, 3D Studio, Micrographix, or something similar.