If you have a web site and a blog site, chances are that you have two separate Google sitemaps that list the URLs within each site.
If you have two or more domains then we have to maintain more Google sitemaps within the domain and there is no easy way (i.e. a tool) to generate a proper sitemap for all the pages within our sites.
If you do have two Google sitemaps (contained and managed within the same domain and hosted on the same server), then I have enhanced a PHP script to read these two Google sitemaps, extract the URLs and then parses and appends these links into a file (called urllist.txt) that is read by Yahoo, MSN and Windows Live search engine bots.
This helps Yahoo, MSN and Windows Live Search search engine bots to find and index your site pages and aids Search Engine Optimisation (SEO) as they can find your page URLs more easily.
The script was written using PHP/4.4.1 and only tested on Apache/1.3.33 operating system platform.
You are free to download, review, use and modify this PHP script as you so desire.