NETGEAR WMA1100 is the only working WIFI dongle for EV3
At TechnicBRICKs there is also some good information to be found with regards to the EV3.
Here is a re-post about WIFI Dongles and EV3: (thanks Fernando)
Similarly to what happened with BT dongles for NXT, there is a very limited choice regarding working WiFi dongles for EV3. Until someone changes something in the firmware/VM executable there is only one WiFi dongle that will work with the EV3. It is the NetGear WNA1100 (with USB ID 0846:9030).
You can find these dongles at the moment at several sources, and eventually at your local retailer too.
USA (19,95 USD) Amazon.com
Europe (12,99 euro DE, 13,95 euro NL, 11,90 pound, UK) pixmania.com (select your country) then search for "netgear-wma1100"
USA (39,95 USD) LEGO Education (which charges a premium price for reselling this...)
Unfortunately none of the small sized WiFi dongles in the market, or even any other large one like the NetGear dongle, will work!
It has to use a specific Atheros chipset (one supported by the ath9k_htc linux drivers, which limits us to around 20 or fewer devices) and then the VM executable checks for a specific USB device ID (unique to the NetGear dongle) before loading the atheros drivers so no other atheros-based dongle works either. Dongles that use Ralink or Realtek chipsets do not even have driver support in the standard firmware image.
Be aware, before you get to buy something else!...
Here is a re-post about WIFI Dongles and EV3: (thanks Fernando)
Similarly to what happened with BT dongles for NXT, there is a very limited choice regarding working WiFi dongles for EV3. Until someone changes something in the firmware/VM executable there is only one WiFi dongle that will work with the EV3. It is the NetGear WNA1100 (with USB ID 0846:9030).

You can find these dongles at the moment at several sources, and eventually at your local retailer too.
USA (19,95 USD) Amazon.com
Europe (12,99 euro DE, 13,95 euro NL, 11,90 pound, UK) pixmania.com (select your country) then search for "netgear-wma1100"
USA (39,95 USD) LEGO Education (which charges a premium price for reselling this...)
Unfortunately none of the small sized WiFi dongles in the market, or even any other large one like the NetGear dongle, will work!
It has to use a specific Atheros chipset (one supported by the ath9k_htc linux drivers, which limits us to around 20 or fewer devices) and then the VM executable checks for a specific USB device ID (unique to the NetGear dongle) before loading the atheros drivers so no other atheros-based dongle works either. Dongles that use Ralink or Realtek chipsets do not even have driver support in the standard firmware image.
Be aware, before you get to buy something else!...
Comments
This dongle works! You need to put it in the EV3-usb, NOT THE PC!
Procedure:
Switch EV3 off
insert the dongle
boot the EV3
Go into wifi, enable it and connect to your HOME WIFI NETWORK
(usually WPA2 enable nowadays)
It works fantastically!
WTF doesn't lego the WMA1100 in the box when its only 15$? I payed a freakin 400 for the kit! And still Bluetooth sucked, with two adviced BT adapters!!
OK, tha's history because WiFi works great!!!!
I agree that the Bluetooth option is very poor.