Why do I get the feeling that you're probably right about underpricing myself :)
for example, asked your rate, just double the amount you thought of. If you build in plenty of ceiling, you can have the other guy look like a negotiation genius to his boss, and you still have achieved your original goal. But don't ever just cut your rates, ask for something in return - IP rights to software, endorsements on your site, just don't cut your rates. (I have, I always regret it)
PS I think tpateck has "don't cut your rates" as a tattoo. :-)
PPS - getting something in return really makes the other guy look like a negotiating genius