Not so much a great place to 'steal' speeches but perhaps a good idea to look for interesting topics to expand upon.
http://www.ted.com/
Ideally because there are a lot of "abstract" speeches at TED , infact if you look at the most viewed speeches they are deal with "inspiration, insight, creativity, motivation".
But realistically, since they're just looking for good speech form regardless of topic. Pick something incredibly interesting to you that's preferably understandable by most audiences (by which i mean. Don't talk about minecraft/games or anything down
that route).
Personally i think speeches on the environment/global warming have been so done to death that the mere notion puts me to sleep, theres a metric ton of more relevant speech subjects concerning the future of our generation that you could talk about. Short list of easy to write topics
Teaching as a skill unto itself: (The value of enthusiasm & creativity. Theres 101 sources you can quote here, from studies to accounts by famous individuals)
The art of communication: And its value in all walks of life. It's a pity because if you had time i'd direct you to
this book
If you want something exciting from your perspective popular routes would probably be
War -
Technological advances in warfare: Drones, robots designed to run on "biofuel" (corpses), etc. Endless field with interesting applications.
Physiological effect of drone piloting: Drone pilots often basically drive to work then drive back home for the day after potentially killing a number of people. Its an odd concept to most.
Modern propaganda: Extensive field, most modern news services tend to put a spin on things and play on public fear in war.
Cyber-warfare: In particular the use of industrial viruses such as
stuxnet or the increasing use of cyber-espionage to lower the potential damage of individuals (see
operation cupcake always good for a chuckle).
One interesting topic that, i guess you could construct a speech on albeit a little random, something that is aw being discussed recently, was what the world would be like now if it had stayed as a single continent (e.g,
Pangaea) as one of the possible suggestions is that due to the lack of ocean divides, all war and cultural difference would have ended fairly shortly compared to modern day leading to a far more technologically advanced society (potentially), and that we would all be of one culture/'grouping' and 'probably' significantly more advanced. There's also the non-discussed areas however like the effect of plague (what would the
black death have done if it was one giant continent with no borders?), would religion have suffered the same decline as it has now if only one religion had the potential of dominating the planet? would the lack of war actually hamper our technological progress? etc.