Flash adds interactivity and features to your website. However development of Flash content requires good knowledge of Adobe Flash , it license and ofcourse time. If you choose to buy Flash applications that can be costly, so what's the way out. A good amount of flash apps, widgets etc. are available free of cost as swf or fla files. Check out some of these websites.

• www.actionscript.org: This site is a well-designed, comprehensive
  resource on ActionScript. It includes extremely active discussion forums
  (with tens of thousands of messages); more than 200 tutorials on
  ActionScript at beginning, intermediate, and advanced levels; a library
  with more than 600 ActionScripts, more than 900 Flash movies, and
  more than 40 components; links; and an employment section.
• www.flashkit.com: Flash Kit is probably the largest Flash site, and it’s
  up-to-date. (We define up-to-date as having Flash CS3 material within
  days after it has shipped.) You can find thousands of .fla files to download
  and study, hundreds of tutorials, dozens of active discussion
  forums (some with hundreds of thousands of posts), links, thousands of
  sounds, more than a thousand down loadable fonts — if you can think of
  it, you can find it here.
• www.flashgoddess.com: Flashgoddess is an informative site showcasing
  women who do brilliant work with Flash. It includes profiles of and
  articles on terrific Flash designers, a gallery of work by featured artists,
  a listing of women speakers, links, job listings, and more.
• www.flashmagazine.com: This site includes news and reviews of
  Flash and Flash-related products. You also find links, articles, and a list
  of hundreds of applications that can output Flash Player files.
• www.gotoandlearn.com: This is a site containing dozens of terrific,
  free Flash tutorials on video, developed by Lee Brimelow, a Senior
  Design Technologist at frog design.
• www.kirupa.com: This is MIT student Karupa Chinnathamei’s site
  about Flash and other Web technologies. It contains more than 100 tutorials
  (many of them on video) and discussion forums with thousands
  of posts.
• www.ultrashock.com: Ultrashock is a multifaceted site that includes
  tutorials, downloads of more than 200 .fla files, and discussion forums
  with more than half a million posts.