I sometimes struggle with some of the aesthetic design aspects of building a website. However, in times of despair, I cheer myself up by looking at examples of the worst web design. It is a comfort to know my efforts are nowhere near as bad!
This badwebs example has been around for a while now, but it still sums up some of the worst annoyances.
The worst website shows how annoying pop-ups can be. It is a bit of a prank and will temporarily disable your browser! (If you really can't bear to click your way through the countless pop ups, you will need to start windows task manager to shut down the browser.) However, the alert bomb will only happen once in 24hrs, so if you revisit the site on the same day - no pop-ups Phew!
I also find Vincent Flanders site a highly entertaining way of learning good design from observing the bad. (So good in fact, I've included a link on my web design resources page.) This Havenworks one from his 2008 selection is just so unbelievably bad!