Ticketmaker
Make your own official-looking tickets for any event. Note that these are just for fun — don’t try to get yourself into a concert with them. I highly doubt that the “barcodes” will get you past the security scanners. If you do try, you didn’t get your ticket here.
Just fill out the form and hit “Go”. A PDF will be generated for you to download. The PDF contains a 300 dpi ticket and should print easily.
You may be interested in the generator at says-it.com. Their version is quite a bit more sophisticated, but sometimes it’s not available. I’m also not sure if theirs is print quality.