I've noticed with Windows Servers you can limit the amount of requests or hits at one time to a site. Say like have 60 people browsing and when it reachs that limit it stops pages being served till it drops below this limit.

Is this possible?

Or limit the amount of mysql requests per account.

Any of this possible? or to limit any other service?

If this is possible how do you set it up?

Would it be possible to make it so certain sites can have more requests than other sites?

Limiting traffic depends on whether or not you are using multiple IP's. On the RAQ, bandwidth is limited to unique IP addresses. If you care to learn Linux, you can limit things further using various tools for linux.