QUOTE(guaranteedconstruction @ Aug 15 2012, 08:31 PM)
There is no limit technically however you don't want to seem like a keyword spammer to Google.
Max 20 Keywords.
Average site is optimized for 5-7 keywords max,
Seriously? So you're saying that Amazon is only optimised for 5 - 7 keywords?
OP, try and optimise your site for as many keywords as possible and don't worry, doing so IS NOT seen as 'keyword spamming' by Google.
Create multiple pages with unique content of 500 - 1000 words and above per page.
Each page should target 1 x primary keyword plus a secondary keyword or two.
To stay below the radar keyword density should be no more than about 2% - 3%.
Longer content = more knowledgable & more pages = higher authority in Googles eyes.