If you're hankering to join the web startup circus and have everything but an idea, here's one for you: a full-on desktop publishing app ... online. The ready acquisition market for decent online productivity apps can serve as inspiration, even as the insane complexity of the undertaking urges you on toward greater heights of caffeination and maybe some anti-depressants.
Seriously, apps that can deal with complex page layouts and can produce a variety of press-ready output (InDesign, QuarkXPress) are expensive and hard to learn, and the average person rarely needs them. It would be nice to be able to hop on a web page and do a quick design. Wizards or integrated help could go a long way. All the usual business models (adds, freemium, pay-per-storage, etc.) apply.
Now, if you build this in Flash/Flex or in Silverlight (2.0), you merely have a ton of work ahead of you. While challenging, you may feel like you're not ... well ... proving just how wicked you really are, since those two platforms give you all of the technical infrastructure you need.
Here's a hint: one of the tricky bits is measuring text line layouts, since you'll need to make sure that the view matches the backing data (from which you will be generating other "views" or output formats).
While you can't ask these things directly, the clientHeight DOM element property can be useful: it shows the actual height that a DIV's content will lay out at ... so it will also signal when content has flowed from one line into a second line. By hiding the DIV, rigging up a while loop, and monkeying with the content (string), you can build a routine that measures text, so that you know exactly which characters are going to appear on a line.
Completing the application is left as a (possibly lucrative) exercise for the reader.