I played around with Webduino library and I think that I will release the final code after replacing ENC28J60 with a W5100, using standard ethernet library and webduino instead of ethercard lib. It's just to complicate and memory-intensive to handle multiple subsequent ethernet calls with ethercard lib (I had to implement a message queue), so for this reason I decide to try to use the W5100 (9$ on ebay) that will make me able to develop a much more stable and nice interface. I hope to put it online in some weeks (I'm waiting for the W5100 shipping :))