Here is a site mentioned to me when I was at the Society of Genealogists earlier in the month. It was new to me and contains genealogy databases from Britain, Canada, Australia, New Zealand, USA and a few more categorized under the headings:
A word of caution. Although the site is free there are pop-under windows that appear using IE7. The Firefox browser suppresses them, but I did notice a flickering of the cursor, possibly related to the suppression. I recommend ensuring you have solid virus and trojan protection in place before trying these links.