I have heard this question few times and I wanted to share my thoughts on it. The two questions are: Is there anything special that MOSS does to crawl pages with iFrames in them? Or do we have to do anything special to get MOSS to crawl these pages?
The answer to both questions are not really. MOSS crawler simply does an HTTP GET against the URL it is pointed to. It takes the response and indexes all the content in the response using an IFilter. So in this case, the crawler would be able to index all the iFrame children as part of the containing document. Children being the source that the iFrame is pointing to such as iFrame SRC="URL"’. There is no special configuration needed to enable this.
Hope that helps