Possible sources of presentation topics
Some suggestions, via John Wilkins at Ohio State University:
From Science, What we don't know: 125 top questions
Intro and 25 questions
100 more questions
Here are some recent new "physics ideas" in the last few years
Physics News Update
Physical Review Focus
Physics Success Stories
Alternately, looking at what now counts as a great discovery over a
longer time span might stimulate you with respect to recent ideas.
Important inventions in the last 2000 years
Greatest engineering achievements of the 20th century