I have a personal standard of not allowing more than 10 usually just because I like to keep the strength of each page, but 20 sounds about right for most people.
in a google document I read a few years back its says 99 outgoing links. But I think if you want to keep a page strong no link at all is the best policy as each outgoing link take a little bit of PR away so the more link the less strenght
You can have any number of links (max 100) from your home page It will not have any bearing on your page rank but it will affect the page rank of the website which has links on your website To prove this see this website www.indianwebdirectory.info its page rank has been updated to PR3 from 0 and it has more than 60 odd links so the no of outgoing links will not affect the page rank of a website
The less,the better! Personally I wouldn't put 15+ outgoing links on a page unless they have nofollow attribute.