I would think: A lot of creativity and a vector draw program.
Because to use a logo in many different variaties it should
be scalable with no quality loss. Maybe you should try Inkscape.
Thorsten has a good idea. If you want a "quick fix" then there are
literally dozens of free banner creation services on the web. I just
did a google search and found a few. The one I've used most often is
CoolText.
**Caution: At least one site I opened in this list was a highjacker
site. I'm safe from that but you may not be. Be sure to go to a good
browser test site if you are concerned. I recommend Scanit.be. http://bcheck.scanit.be/bcheck/
Here's the search link if you'd like to look around.