I also recommend paying the $300, but keep in mind that your business name will become your site's title for all Yahoo searches. If you have a reference site, you can get in for free, but I wouldn't count on it - esp if you have a bunch of affiliate links on your "reference" site - and it takes forever.
I wouldn't bother paying for a listing - I seem to be doing just fine in the SEs and I am listed in neither DMOZ or Yahoo.