I've used a few approaches: 1) BCC (old design): Grabbed an appropriate template from oswd.org. Chopped the heck out of it. Cost: free, but spent quite a bit of time. Quality: it didn't scare people? 2) BCC (new design): Found a very talented young lady in India on elance. Cost: a few hundred bucks. Quality: I won't win most-beautiful-site-ever awards, but the cost performance was outstanding. 3) Appointment Reminder…
Getting 3 themes at WooThemes will run you about $70. Those three themes each come in several color variations too. That means the next 3 times you decide to throw up a website, it should take almost no work (design-wise). WooThemes is really easy to use and customize, and they have good documentation.
This makes throwing up a sales site really easy. Effectively, any time I create an app, the first step is to put up a WordPress site with a WooThemes theme, build up the copy/etc, then copy the design for use in the actual application.
Note: I usually host my sales site on www.MyAppName.com, and have my "actual" application (a Django app) running from a subdomain like app.MyAppName.com. This way, I host my WordPress sales site completely separately from my app, which is easier for me to manage and to not screw up.