Updating an old thread, there are new official tile server URLs as of this date:

http://a.tile.opencyclemap.org/cycle/%0d/%0d/%0d.png
http://b.tile.opencyclemap.org/cycle/%0d/%0d/%0d.png

(from http://wiki.openstreetmap.org/wiki/Tile_servers)

edit: I've just noticed there are lots of "new" repositories on Mappero, after clicking the Sync button on the Maps > Repositories dialog. Does anybody know where Mappero is synchronizing from? Is it possible to add the OpenCycleMaps repository to this elusive sync source?