I simply aren't able to find the number of applications you are able to host on heroku with one dyno?
I intend to host lots of small applications with little traffic.
Dynos are calculated on the per application basis.
However, this does not mean you have to buy 3 dynos to operate 3 applications. You may create 3 application each with 1 dyno.
One Application per Dyno / subdomain.heroku.com.
Some explanation here: http://paperwork.heroku.com/performance#backlog-too-deep