1. They are pretty similar in some ways but have different interfaces. Blog is a list of articles (posts) authored by one or more persons and with the ability for others to comment on - and comment on each other comment. Forums consist of threads - people can create threads and others can post replies in threads.
The best way - create both and play with it.
2. We already have some of that. Anything specific you are looking for?
Dmitry Buterin, Chief Apricot