Upshot: Here is your intermediate guide to HTML5 Geolocation-centric APIs. Pros: Another straightforward O’Reilly intro to HTML5-like cutting edge hotness. Cons: None really. Code might change over time, so get the eBook for free updates.
If you need a quick introduction to Geolocation APIs available from Google, as well as ArcGIS, then HTML5 Geolocation is it.
The author also does a nice job of outlining just what Geolocation is (it’s not just a flat 2d map), what resources are available, as well as what resources can/need to be saved, and what you can do with that information. The breakdowns of the geo-specific code are very straightforward, and there is a LOT of code, so I recommend getting the eBook version.
Finally there’s a section on marketing & privacy and whether that still matters to the younger generation —and how/why all this social network-spacial relationship stuff works in context.
Disclosure: I received the eBook download from O’Reilly for review purposes.