Toastmasters International. It's got nothing to do with bread, but rather the kind of toast given at a wedding. To give a good toast is to elevate those around you, encourage feelings of goodwill, and share a thought worth remembering.
Toastmasters is an International leadership and public speaking development club, and above all other resources, is the one I recommend the most. Going on and on about technique and tips for public speaking is of no use to you if you don't find a supportive, fun, and engaging environment to practice speaking in. The people you meet in Toastmasters (and you'll find the same if you visit other clubs internationally), truly wish to see you grow and will help you in your journey to developing your leadership and communication skills.
I cannot recommend Toastmasters enough. It has been and continues to be a source of mentorship, comic relief, moral support, wisdom, and inspiration to me for over 3 years now and I always leave the meeting feeling better than I did walking in.
To find a local club near you, visit the Toastmasters International Find a Club page.
This is a free, self-paced online course on public speaking. From preparation to delivery, no matter your level of speaking skill, this course can teach you some excellent things about an activity many people place among their worst fears. The difference between written and spoken language is a particularly useful lesson from the course.
As a business student, I'm used to preparing, delivering and watching multiple presentations each semester. This is one webinar that could solve a lot of engagement problems plaguing those presentations and is worth checking out. Even if you feel pretty good about your presentations, your audience will appreciate the extra thought.
Vulnerability in Speaking
Scientific American article on using your nervous energy to improve your speaking.