There have been over 350+ submissions to the 10K Apart contest conducted by Microsoft & Event Apart that has a prize money of over $10K.
The important rule was that participants should build a web app whose total file size including images, scripts & markup, shouldn’t be over 10K. All code must run client-side although 3rd-party Web services & JavaScript libraries like jQuery, Prototype & Typekit are allowed. The code must be standards compliant & usage of HTML5 is encouraged.
The submissions are good learning material for developers who value speed & standards. They are listed on the home page. Sort on the Highest Rating & Most Comments options (generally good indicators of popularity) in the dropdown box there, to get started with viewing the apps & their source.
Update (14-Sep-2010) - Hakim El Hattab's game measuring a measly 6.9KB has won him the grand prize of $3000 & other goodies. The entries of the other 3 Runners-Up are addictive games that you better not check if you don't want to waste time.
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html5,
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jQuery