Multiple I2C devices on Arduino
You'll see that I've used 10k resistors on each devices's SDA and SCL lines, but is this necessary? I've seen it mentioned on a few online documents for certain breakout boards etc...


You should have just two 3.3K resistors - one on the SDA and one on the SCL lines.  However all your 10K resistors in parallel will equate to about the same thing - just taking up 3x the space.


  Also, are the devices just connected in parallel?


Yes, it's a simple multi-drop bus.


  Are there any considerations I need to make when using 3 I2C devices like this?


Not really, no.  The frequencies in use are generally too low to require any specific layout considerations. Just try to keep vias to a minimum and don't snake the traces around the board too far.