Folksonomy is a system in which items are collaboratively tagged to categorize content. In simple words: Multiple users tag an item with terms, and as such will it be identified.

you can use RSS Feeds

That's a tricky one. I see several possible ways to go here:

1. Use an established taxonomy of skills (say from the Bureau of the Census). Tweak it as you go along.

2. Start running the database allowing any folksonomy tag to be input. After a while, collect statistics on the most used tags, either keep them as a folksonomy with, say, a suggested list, or try to build a taxonomy using the list.

3. Analyze your domain in advance and build a taxonomy. Please see Clay Shirky's claim that you do not need any taxonomy in the links.

Folksonomy is a system of tagging, cataloguing or arranging items by means of a collaborative effort. While this does apply to websites that are affiliated in World of Warcraft (such as WoWHead, WoWPedia or MMO-Champion) the people playing the game don't really have much of a say in the categorization of items/NPCs/locations in the game world.

The closest one would get is probably the fact that MMO-players have a distinct vocabulary, which might allow for classification, but there's no ability for players to "tag" items for others to browse.