CN Tower
Niagara Falls
Golden Gate
Mt. Fuji
Great Wall
Grand Canyon
Hoover Dam
Pyramids
Petra
Colosseum
Leaning Tower
Parthenon
Stonehenge
Big Ben
The Chunnel
Eiffel Tower
Mt. St.Michel
Empire St Bld

Alaska glacier
Tokyo Tower
Forbidden City
Sum'r Palace
LaBufadora
Bilbao Museo
BlarneyStone
Disney Paris

Trip Stats
With my consulting background, I can't help but to "go consultant" with some trip stats combining my EuroMediterranean and Asia segments.

1.  Vary your travel 
I had a nice mix: solo travel, tour groups, traveling/staying with friends
Travel Days

2. Mediterranean Cities are Cheaper
Southern Europe tends to be cheaper than Northern Europe.  And what they say about Norway is true:  Oslo is the most expensive city.
Expenses per day by select City
Note: Yes, I did actually keep track of everything I spent by these categories.
Only these cities are included due to comparable lodging and food quality (well, except for Rome, where we stayed in a posh hotel near the Spanish Steps).
Transport = travel within the city, including airport transfers, subways, and taxis.
Other = Tours, museum/attraction fees, Internet (about $5/day), but excludes souvenirs.  Paris Other is highest thanks to Moulin Rouge ($79) and Disney Paris (~$33)

3.  Ancient attractions are cheaper
Thankfully, attractions don't charge by number of centuries covered.  In fact, the oldest attractions, like the Colosseum and world famous Louvre, Prado and British museums, are the cheapest.
Note: Prices in US dollars or Euros for Euro countries, since they're close now

4.  Meet fun fellow tourists frequently
Oh the people you meet traveling.  It's fun to hang out with the many friendly Aussies roaming through Europe.  Older couples offer great travel advice and tell it like it is.  Unfortunately, packs of loud American college girls on break who say "like" a lot swarm like locusts.  You'll hear 'em especially in Paris, Spain and Italy during spring and summer break, speaking English loudly, and mangled French/Spanish even louder.

5.  Try the McDonalds Difference
If you really, really have to, you can still get your fix of McD's cause the Golden Arches are everywhere.  The basic menu is the same, but prices vary.  At least, try the local adaptation menu item