Ethernet W5100 Shield Network Expansion Board w/ Micro SD Card Slot for Arduino

Pros: very good quality, easy to use also for beginners, good SW support on www.arduino.cc pages and nice tutorials with lots of examples

Cons: is not in zero level with the main board due to legs but this is only aesthetic fail (couple of bundled support pillars would do the job, common 3mm screw is too big to fit there), SD card needs quite a lot of pressure to get in/out

Other: didn't come to testing of SD card yet, hope it works well

Pros: Fits as a shield, tf slot works like a charm (no use of pin 4 anymore!). has no mac address (make your own) more than enough status led. easy access to cheap memory (tf) it contains a reset button.

Cons: has no mac address label, if you push the Ethernet connector down it can touch the usb connector, my advice is to use some distance holders or put a piece of tape on the usb connector (like i did). no use of the led 13 anymore :(

Other: use sd.h and Ethernet.h from the arduino examples, they are fully compatible.