http://www.amazon.com/Business-Plans-Dummies-Paul-Tiffany/dp/0764576526/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1201616273&sr=1-1
While it is a "Dummies" book it was required reading for my Venture Capital class in grad school. I still have it on my shelf at home. It provides useful guidance on how to develop and write a business plan. If you have no experience with business plans then I highly recommend it.
I don't remember if this is addressed in the book but you might also want to work on your "5-minute pitch." Basically, when trying to get money from a financier you should be able to summarize your business model, products, required investment, and (most importantly) how you will recoup that investment (return on investment) in a 5-minute pitch. This speech determines whether the venture capitalist wants to hear anymore about your business idea. Anyway, I am not sure if the SBA will need to hear this sort of thing since I think they deal mostly in loans, but just an FYI.