Hi Luis,
I tried several options via http://alternativeto.net/software/idisk/
I installed Wuala, which is free but is limited to 2GB, as is Dropbox. And if I look at the prices, I am not too happy.
Now I am working with Nomadesk (http://www.nomadesk.com). I went for a single fileserver which costs me around the price that MobileMe costed me. And ... with unlimited storage! I use nomadesk for half a year now. It is ok.
Nomadesk sync all your files (Windows and Mac) to three computers. Sharing of files is possible, as is sending a file link. However, you don't have a public space as Mobile had.
And, Nomadesk is really reliable. I guess there will be lots of developments going on for the coming months. Free space will increase and prices of online storage will drop.
Take your pick!!