Building/Submitting a site map

My site has been submitted and is being 'crawled' by some search engines.  Google, however, asks for a site map if it can be provided.  I would like to give them one, but am not sure exactly what they are looking for, how to build it, or what all it needs to include.  Can someone explain this to me a little better?  Is it even worth my time?

Travis

Thanks, Ryan.  I will check out the links.  I was able to register on Google for free, can I do the same on Yahoo and MSN?  Everything I found on their sites makes it look like you have to pay.  I already come up on searches there, though.  What is the advantage to submitting my site to all these search engines?

Travis

And thank you very much, again.

Travis

A robots.txt file was originally used to "suggest" to crawlers what sections of your site you didn't want indexed.  There's no spec that says they must follow your requests.  But if you have pages you don't want indexed - login pages, private stuff, that sort of thing - you can include them.  But you probably want your entire site indexed so don't worry about the Disallow settings.

You can get by with a single line
file.