Yahoo UI Library

Yahoo! UI

Pros
  • simple AJAX
  • Drag 'n Drop
  • Visual Effects
  • Event handling
  • Widgets
    • Autocomplete
    • Slider
    • Calendar
    • Container (tooltips, panels, dialogs, etc...)
    • Menu
    • Tree View
  • Excellent documentation
  • Modular approach (many small files)
  • small possible footprint (10KB)
Cons
  • Possible heavy footprint (200KB+ if using many features)
  • Verbose scripting (yahoo.util.effect.*)
  • Lacking innovative features

Differentiators

(plus) Excellent Documentation
(plus) Small file sizes
(plus) Cool widgets
(minus) Long scripting namespaces
(minus) Lacking innovative features

DEMO: http://developer.yahoo.com/yui/