YARD allows you to use Markdown or Textile to write your documentations, provides structured tags to better describe your methods and has a very advanced parsing mechanism. It also under active development, which is a very good sign of interest.
Back in September I asked for feedback about using Yardoc over Rdoc and YARD won with full consensus.
I'm now proud to say that the master branch of the Whois library is now entirely documented with YARD. It took several weeks, but I'm really satisfied with the result. I also had the chance to fix several documentation errors an increase documentation coverage.
In the meantime, you can try it yourself by downloading the library from Github and using the YARD server, an other awesome YARD feature.
$ gem install yard $ git clone https://github.com/weppos/whois.git $ cd whois $ yard server --reload