Google have in beta a tool called Google Trends that allows you to look at trend history for search terms. You can also compare the history of multiple search terms. It is really interesting to see the increase in some search terms:
blog wiki - Just shows how the awareness of blogs and wiki's has gone thru the roof.
lotus notes microsoft exchange - Lotus Notes is Seached for more than Microsoft Exchange however both have declined.
asterisk - This is interesting in that we have been running up Asterisk servers etc.
Pretty interesting stuff.