Apple - View the current clock Speed of a CPU in OS X?

There is a tool that does that called Intel® Power Gadget.

It will show the current load and Frequency

And Version 3.5.3 on macOS (latest is 3.5.5):

well there are two ways, if you want to see your processor load you can check activity monitor.

but if you want the actual frequencies here "Intel Power Gadget" is what you are looking for: (thank Yevgeni for the link)

(UPDATE: APP MAY NOT WORK PROPERLY ON NEWER LAPTOPS os x froze on yosemite)

i just installed it to and it works GREAT

(side note, if you want super accurate readings, keep in mind, the intel application itself, uses some (altho minimal) power)