Where are the best places to buy scientific equipment?

[Simfish]

So I'm mostly talking about things like digital thermometers that i can use everywhere, pressure gauges, humidity sensors, and chemical sensors (especially sensors of CO2 levels, O2 levels, particulate matter levels, and maybe things like decibel sensors). Just for plain curiosity. :)

Thanks!

 

[dlgoff]

Some of the sensors you mention can be found here.
http://www.omega.com/"

 

[Chi Meson]

Check out the Vernier Lab Pro.

 

[waht]

http://www.used-line.com/