One picture says more than 1000 words!
It gives a much better clickthrough and it is much clearer for users when there is a little screenshot of the website. E.g. when you have a linkdirectory or even a linklog it is worth accompanying some of them with a thumbshot.
Ofcourse you could create your own screenshot, resize it, upload it and then show it but, as always, by thinking component based you will build your site the most efficient.
example:

LEAU.NET a cool weblog

google!
Get the code at
thumbshots.org.
What are Thumbshots thumbnails?