How many websites are there on the internet?

This will give you a rough estimate. Note: this is just including
domain registrations, so all the Geocities sites 12 year-olds make
aren't included.

29,011,514 - .COM
4,752,602 - .NET
3,003,090 - .ORG

Source: http://www.whois.sc/internet-statistics/

Very well, NDogg, but what about the many (for example) .co.uk sites? The .edu?

if you go to google.com on the bottom you will see "©2004 Google -
Searching 4,285,199,774 web pages" - this will give you rough estimate
of WEB PAGES!

"With close to 407.1 million users, 33,942,187 domains, 25,675,581
websites and over one billion pages, the Internet is nothing short of
an ocean when it comes to information."

http://www.expresscomputeronline.com/20030616/indtrend1.shtml

Well the Netcraft web server survey shows that there are 55million
hostnames with 25million of those being active sites. That is not an
exact list of web 'pages' but is a pretty good indication of how many
web servers are around.

There are some interesting statistics and trending shown at:

http://news.netcraft.com/archives/web_server_survey.html