Lichess is a cool online chess site. Although, it is not, as it claims, open source: it places non-commercial use restrictions on the code, for example, failing the open source definition.
Its easy to write simple web applications quickly with Webpy. Can parse C99 with open source parser (pycparser) implemented in Python, and display the generated syntax tree in a web browser via JSTree. Hence a very semi-working OpenCL lint tool (just needs, hmm, a proper preprocessor, symbol table, type-checker to do this right: not going to do that outside the day job, obviously!).
The graphics support in browsers is getting better: Graphviz display in the browser via canviz, and some ease of use APIs over the HTML5 canvas (EaselJS) element.
Maze generation. Nifty CS assignments I wish I had on my course. Key events in JavaScript. If this script works, and the web-service it uses is any good, finding plane tickets should be easier.
With the somewhat more extreme climate around, weather seems more interesting. See also wview.
For journalism, and print media that 'gets' the internet, the Economist is pretty good; a print subscriber gets the same content online, and in an iPhone App, and in audio. It's rather like distilled BBC Radio 4.
