Here is a link to the
Wikipedia and Flickr nofollow plugins. They are each small php files and just dump them in the main "plugin" directory and activate as normal.
The only directories I provide buttons to on my site are ones that score in the top 200 for "travel blog". They are also pseudo traffic checkers, so I can at least compare my traffic to other similar sites. They also tend to bring in about 1-3 visits per day to my site. (however, some really underestimate my traffic. There are some sites I know in the bottom of my soul I get more traffic then, but they out rank me on those lists).