Gated Content and Search Engine Spiders

I am working on a new web site that requires users to enter their zip
codes before we provide any content to them.

This has caused an issue with some content that is behind this "gate"
but is not geo sensitive. I would like to allow the spiders to index
this content so users could find the information that is there when
they search.

Is there a way to allow content to be indexed by search engines and
require users to enter a zip code to get to it?

Many Thanks
Scott