Posts will be a little slow this week as I'm not very well - party season has taken affect (!).

2010 will be much more substantial.

XML sitemaps are a great way to improve indexing, we know that. But, what if you have a really large site >100k?

You can't have more than 50k pages within a single sitemap so you've got to split your site into sections and implement a multiple XML sitemap strategy.

To do so you need to look beyond the free sitemap generators that have a 500 URL limit and download a dedicated sitemap generator - I'd recommend GSite Crawler for functionality, but perhaps not for speed.

1. Split your site into relevant sections - homepage+top level categories, departments, products sundry pages.
2. Create an XML sitemap for each of the sections.
   
3. Adjust , and settings to reflect page changes and importance (n.b. remember priority settings are relative to your site).
4. Create a sitemap index file that links to your multiple sitemaps - view example
   
5. Upload via Google Webmaster Tools.
   

It's worth remembering the focus here is on getting you deep pages indexed. A web crawl should find and index the majority of your top pages so it's worth spending extra time on planning and implementing product sitemaps that prioritises areas of the site where your sites architecture may not complement.

Remember earning good links (PageRank) and Information Architecture are still the most important elements to focus on when looking to get your large site indexed.