I have may ideas for projects that require ethernet connection, it's too awkward and expensive to use an ethernet shield.
You can use a serial connection to a PC that has an internet connection and use the PC as bridge. Almost all prog languanges on a PC support serial ports so ...
The netduino plus has ethernet but I'm not sure that I want to use .NET.
FEZ is also a .NET based solution, that is (more or less) hardware compatible with Arduino shields. www.tinyclr.com
Is an Arduino version planned with ethernet on board?
This is exactly why i develop my custom arduino like pcb It contains enc28j60 chip, digital thermometer and configuration reset button on unused (by arduino) analog pins.
However, i can't tell you when it will be available
You can use a serial connection to a PC that has an internet connection and use the PC as bridge. Almost all prog languanges on a PC support serial ports so ...
I know but I want to have separate boards in different rooms in my house, with ethernet connection to get/put data directly or through my linux server that is always on and can process data more intelligently when required. Don't want PCs everywhere...
An Arduino with LAN or WLAN on board is the ideal solution for me.
I believe the Arduino team is working on the perfect device for you:
There is a blog post with a picture of an early prototype on the Arduino blog titled: "Arduino Ethernet And The Gym"
At the Arduino Uno event at NY Maker Faire, they talked a little about it and said that it could be powered over ethernet (real POE) and also be updated (programmed) over ethernet.
I don't have any details on when it will be available, but I sure will get some when they are.
I have a netduino and a fez panda and have developed in .net quite a bit outside the boards. I still use arduino for everything as I have yet to be able to accomplish the same level of implementation with the .net systems as I do with arduino. That said - port write speed is very slow without "going native", which was a show stopper for me. If you don't need fast port write speed and like .net - it may work for you.