Whenever a new version of Wordpress comes out (as just Wordpress 2.6 did), it is somewhat of a pain to upgrade it.
But not for me anymore, because I have created a small (and simple) script some versions ago which I would like to share with you.

$ cat upgrade_wordpress.sh
wget http://www.wordpress.org/latest.tar.gz
mv www wordpress
tar --overwrite -xzf latest.tar.gz
rm latest.tar.gz
mv [...]