phpSitemapNG is a free Google Sitemaps generator written in PHP, but also generates RSS-based, txt-based and HTML-based sitemap files. It will spider your website and also your filesystem (of course, as you prefer). You can download and use it for free, the licence is GPL.
You can try the demo crawler to get an impression of the quality of the crawling engine and also create an initial sitemap.
Please note that this software is not developed anymore and only available “as is”.