You can download a Forms Based Authentication (and COOKIE, for that matter) 'quick fix' or SharePoint Server 2007 Search. It will allow you to create crawl rules using FBA. I mentioned it in a past blog, but many have missed it here http://mindsharpblogs.com/ben/archive/2007/10/26/3305.aspx .
First, you need to download the FBA QFE here.
Second, you must configure an XML file to define the authenticaion provider and login info for the content source. It is well documented in the download from Microsoft.
Third, you run the downloaded 'addrule.exe' command in the format addrule.exe input filename.xml
Ben
Ben Curry, CISSP, SharePoint Server MVP
Mindsharp
http://mindsharpblogs.com/ben
http://www.microsoft.com/mspress/books/10623.aspx