If you need to create a prototype of your website layout and you're in a bit of a hurry, Marvel may be just the solution you're looking for. It’s quite gloriously simple and straightforward: you link it to your Dropbox account (it promises never to anything to your files, ever), you sync it to your chosen mockups or wireframes, and then you show it where the buttons are and tell it which image to click through to.
If you’re in the mood to show off, it even has a selection of fancy transitions that you can apply before saving your finished prototype and emailing off a link.