I've pulled together a Mac search engine optimization and marketing site trying to tackle Mac SEO and SEM programs and issues for Apple Macintosh webmasters. A small handful of the commercial SEO apps are cross-platform compatible, but many if not most others are strictly Windows based. Apple users are often forced to do more things manually.
Particularly when it comes to tools to automate IM - internet marketing and backlink building aspects - Macintosh users have more of a challenge. Its tough finding Mac compatible SEM & SEO software to automate social bookmarking, directory and article submissions on a Mac.
Some trends are encouraging: 1. Apple's growing market-share is increasing the demand for - and profitability of providing internet marketing and SEO optimization tools to OSX using web masters. 2. Cross platform technologies like Adobe AIR are allowing write once, run anywhere code. MarketSamurai is a good example of a PC/Mac tool for website owners on either platform. 3. Worst case, you can invest in a legit Windows install disc and use either BootCamp - or install VMWare or Parallels to run those Windows-Only apps if you have to.
Check out my Mac SEO tools blog - as I unearth and share the best Mac SEM tools, SEO tips, optimization methods out there. There's also some great Firefox buttons and tooolbars and Safari 5 Extensions for SEO that I'm discovering to promote and market my sites with - all done on a MacBook!