I was wondering if startups don't have the marketing and sales expertise in-house (between the partners) and don't want to hire full-time talent, are there any websites that you can look for them?
If you haven't already, make sure to check out What Blogs + Websites Have Provided the Most Help for Your Startup? and What books do you recommend?, as both of those topics will give you a good starting point on where to look for information.
But I believe your best information will come from a good business coach: someone who knows enough about sales/marketing to get you talking to the right sales and marketing people. Out of all of the professionals I've worked with, sales/marketing folks were the most challenging to pick. I suspsect a lot has to do with the difference in each industry (marketing software vs. marketing widgets)
There is a good discussion on How do you find good professional help?, and here's my two-cents on the matter: