Is there a wikipedia type website where we can practice translating/writing stories in Esperanto (and of course, a place where we could get feedback on our work).

They have wikibooks for textbooks but it would be nice if they had something for short stories.

Any ideas?

The only such wiki I'm aware of is Vikifontaro which lets you submit translations of public domain works, which can then be edited by other people. The catch is that the copyright on your work is surrendered, and there is no guarantee that anyone will come along to usefully critique or edit.

Unless anyone else knows of or wants to start such a website, I think the Konsultejo here is your best bet for now. I could try to put a wiki up on Google Sites, but I've never done it before and I don't know how suitable that would be.