I like to read various web articles on my laptop while I'm traveling, and often there's no network available (like, in the air..). I found this little service that someone in the UK setup, which lets you convert any HTML page to PDF. The URL is http://www.htm2pdf.co.uk/, and I can highly recommend it, it's an easy to use tool to make sure you have enough reading material available even when you are offline.
And I know, there are other ways of doing this conversion, but the service above is so far the easiest to use that I've found. There are also web service APIs available, which are not free, so I haven't had a chance to try them.