I saw this at the Catholic Exchange roundtable message board. I've been thinking the same thing lately:
If any of you have any time now or this summer, it would be a great help to have some good Catholics to either write or edit on Wikipedia.com
As you can imagine, there are a lot of embattled Catholic articles on the site and not enough serious Catholic contributors.
For example, the Mother Theresa article has more criticisms of her than positive information. It is painful to see our faith trampled as is happening.
I would not normally think this matters but for every search on Google, a Wikipedia entry comes up on the first page of responses. That is a lot of power to influence the culture.
I'd also point out that a lot of Catholic topics have no entry at all, so they would also be a good place to help give Wikipedia a solid Catholic sense. You need to register as a user, however, in order to create a new entry (you don't need to register as a user to edit an existing entry).