I don't think you should give any bonus for being the first to discover a tech - getting the tech first is reward enough. You can make money trading it, get a head start on building the wonder, etc., no need for additional stuff IMHO.
Now, as for other events...
CTP2 had some good ones, definitely look there.
A few more:
-First to explore your continent
-First to discover all continents
-First to explore all continents
-First to the pole(s)
-First to connect all your own cities by road (minimum # of cities required)
-First to meet all civs on your continent
-First to meet all civs in the world
-First to conquer a city
-First to conquer a civ
-Of course, the ever popular, first to build X number of things (units or buildings)
Also for the reward, IMHO, you never want to snowball the situation. For example, if someone circumnavigates the map, don't give them a bonus to ship movement, they are already in the lead in that regard, give them some sort of science bonus, or commerce bonus - something that makes sense, but is unrelated and won't cause the civ to become better at what it's already best at.