things it could be:
sway bar bushings
endlinks (as tweety said, that'll make more of a 'pop', than a squeek...)
Ball joints
upper strut mounts
control arm bushings or damaged arm entirely
thats about it, other than obvious stuff like a damaged strut assembly, broken spring, etc...those would be more noticeable than just a noise though...
its easy to test the end links and sway bar bushings...just disconnect both endlinks from the front struts...and drive around to see if there is any noise...if the noise is gone, the end links are toast, and the bushings probably need a little grease...at least replace the endlinks (brand won't really matter, all of them share the same annoying design, but i do agree that the 2002 Ford Escape units are a good upgrade)...and try to get some lubricant on the bushings (they're pretty deep in there, but you should be able to reach them...if you still have noise, you know its not the end links...
also, check the ball joints at the bottom point of the suspension (just behind the lower section of the front brake rotors)...that joint should have a thick rubber boot, that is in good shape...if its ripped or torn, or you can see grease coming out...you're getting somewhere...sadly though, the entire control arm needs replaced then...while the joint itself is pressed into the arm, its nearly impossible to find just the ball joint...