As far as rare astronomical events go today's transit of Venus is one worth noting. Especially for those of us in the antipodes. It was to have a gander at one of these that James Cook paddled off to Tahiti in 1769, incidentally 'discovering' Australia & New Zealand on the side (small matter that there were people here already - they didn't know where they were...).
The first to been seen was in 1639, and the time between transits was later predicted by Edmond Halley (the guy with the comet). He also noted that the transits could be used to calculate our distance from the sun but unfortunately didn't live long enough to observe one himself.
The 1760s transits were not visible from Europe so, in the first pan-European scientific venture more than a hundred scientists were packed off to the wog-lands to see what they could see. Bear in mind that in those days a scientist was simply a gentleman with a large enough income to not have to work. Still, they did some impressive stuff.
The transits come in pairs eight years apart, the last ones were in 1874 and 1882 (John Philip Sousa wrote a march for the occasion, 'The Liberty Bell', it was later made instantly ridiculous by Monty Python's Flying Circus), there were none in the 20th Century, and after the second crossing in 2012 there wont be another till 2117. So this is probably your only chance. Unless you're having your head cryogenically frozen (but aren't we all? It's all the rage!).
Anyway, I could go on (and usually do about such boring sciencey things that most people find yawn-worthy) but I've got to get to work. Unfortunately I'll be inside when the transit occurs. Fucksticks.