Flash is an excellent way to produce cartoon animation with embedded, synchronised high quality mp3 sound.
Examples of vector-drawn animation can be found at
You can create just a few elements or a whole website (such as Scott Pilgrim vs The World) in Flash, with multi-media interactivity which is supported cross platform. Many major sites such as Disney use Flash extensively.
It's usually not a good idea for online stores (with the exception of this wonderful Dutch parody at Hema) since not all mobile devices (phones, iPods, iPads and the like) can access Flash yet..
Don't click anywhere in the map below as I have embedded their .swf file on my site so their 'relative' links no longer work!
The minority of computer users who still lack a Flash viewer need just a single plug-in to download. Thereafter they can appreciate every element of the Flash site - an attractive alternative to the polyglot collection of specialised plug-ins for sound, video and animation you might need to emulate a Flashed site using a mix of other technologies such as QuickTime, Windows Media Player, RealPlayer etc. (HTML5 aims to improve this. Google's interactive guide to HTML5)
Adobe claims up to 99% of computer browsers are Flash enabled - though some surveys put this lower. Note that some Internet TVs, games consoles and Apple iPhones, iPods and iPads along with some other smart phones do not currently support Flash - showing just 'plug-in not available' (Flash video can be now viewed as streaming HTML5 via the Skyfire app). Adobe is demonstrating a Flash to HTML5 converter but that will not help existing content.
It is not a good idea to use Flash for your introductions to your index page and all navigation elements without providing an alternative system for those who lack Flash. Also note that while support for Flash is strong installation of the latest version of the plug-in often lags so try to save straightforward Flash work as backwards compatible where possible to increase your potential audience. Newer features such as enhanced video support require newer versions, so test thoroughly.
Flash can use vectors to create fast loading images which can be scaled (without bitmap 'jaggies') to match the user's browser window size. Flash can also render text in your original and perhaps unusual typeface by including the font outlines as vectors, but this prevents the text from being read by a search engine. Versions before Flash MX lacked features to improve navigation and accessibility, leading to Jakob Nielsen's infamous Flash 99% Bad article, written in 2000 and since updated following his consultancy with Macromedia (previous developers of Flash before Adobe bought it).
Microsoft's Internet Explorer has twice changed how embedded Flash content is viewed. Read here for Adobe's suggested workarounds.