If you're trying to max out your internet line then something such as P2P software or a download manager that opens up concurrent connections should do the trick. If configured to use 99-100% of the "available bandwidth" then these programs are going to bring your connection down to a crawl which is obviously not recommended.
Why are you trying to do this? If it's a shared network, this is going to cause ALOT
of problems. Also check with your ISP to make sure they allow P2P and multiple concurrent connections on their network. Many ISPs frown at these since you are "hogging" the bandwidth from their other subscribers.
Edited by NpaMA, 20 April 2012 - 08:32 AM.