Katz, just remember to focus on the benefit you offer to your customers, not on the features or products/services you offer.
So, instead of saying, for instance:
I provide web design, search engine optimization and copywriting services for small business websites.
I might say something like:
I help small business people attract more targeted traffic to their websites, and to increase their revenue by better converting that traffic into sales.
If you know something about what the other person does, you could even personalize it a bit to specifically target their industry. Depends on the exact format of the information exchange, though, I guess, as to how much you're going to know about them before you have to open your mouth.
Once you can distill it down to that sort of 30-second benefit-focused summary, as Barry says, just expand it to three minutes and you should be all set.
(Or maybe you could cheat, and just give your 30-second bit, then get the prospect talking about his business for the remainder of the three minutes.