My site's tagging engine is rebuilding the tags database. Since my site is large this is going to take some time and some features like blogs or search (v6.0 builds dated after 2/1/2008) will be offline until it is done. How can I speed this up?

You can't speed up the rebuild, but you can opt to have the tags that have been processed show immediately, rather than waiting for an entire rebuild.

Go into your Control Panel. Under General Settings, scroll down to the Tagging section. If your site is rebuilding you'll see a link in this section that says "Mark as ready while rebuilding". Click this.