Assuming that you hold a US passport, here are my comments on visas:

Cambodia
Available on arrival, discard above advice
S. Korea
Not needed
China
Best to obtain in HK where it can be done in 24 hours at China Travel Services (many non-US can do the same day)
Vietnam
Needed, some missions can do same day, others, several. BAngkok or HK are probably the best/fastest places.
Thailand
None needed
Indonesia
Available on arrival
Australia
Elecronic Visa done automatically by airline
India
Needs to be done beforehand and best done from the US before you leave. Doing so in the US will get it done much faster and get you a five year visa rather than 3-6 months.
S. Africa
None needed
Tanzania
I believe available on arrival, but not 100% sure.
Kenya
Not sure
Dubai
None needed
Greece
None needed
Turkey
Available on arrival
Egypt
Available on arrival
Croatia
None needed
Morocco
None needed
Ethiopia
No Idea

And a bunch of EU/Shengen zones.
Not needed