Shields that connect via I2C

Folks,

What are some popular shields that connect to the Arduino via I2C? Would you be so kind as to throw some links at me (first thing that comes to mind, really)?

I'm asking because I'm writing a blog post about I2C issues. I'm making my own examples (both: good ones and erroneous ones). I'm also looking for existing things out there that I can use as examples.
[update: Here's the blog post I was writing.]

Best,

  • Nick

A lot of "sensors" have I2C interfaces, whether they are on full shield-sized boards, or smaller breakout-like boards (Seeed "grove", for example.)
I have a Freescale Xtrinsic Sense Board, that is set up to work as either a shield (on arduino-like boads) or a "hat" for Raspberry Pi.

GPS shield. I've seen a few different styles of these. Basically translates the slow, NMEA serial data that is typical of GPS modules to something you can quickly grab via I2C.

Chagrin:
GPS shield. I've seen a few different styles of these. Basically translates the slow, NMEA serial data that is typical of GPS modules to something you can quickly grab via I2C.

I see. So, he basically gives the GPS module its own ATmega, and the latter acts as an intelligent UART-to-I2C bridge. (No schematic, for that shield, unfortunately.)

On a different note, though. Those stackable female connectors on the top side of the shield look amusing. Does he want the user to plug in another shield on top, and block the GPS antenna.

Depends on where it is mounted, the female sockets offer some protection from shorting pins plus give you a place to plug in single wire connections for something else.