Monitor3

Recommendations:

17" Monitors:
Any of Sony's current 17" FD Trinitron monitors with .24mm aperture grille pitch would be a great choice. These include model numbers CPD-E240, HMD-A240R, CPD-G220R, and CPD-G220S. The primary differences are max resolution (1600x1200 on the G220) and the inclusion of speakers (in the G220S).
Other monitors that use the same tube as the monitors listed above (just different case, controls, and possibly resolutions / refresh rates) include the Viewsonic G71F+SB, CTX PR705F, IBM P76, and a few others.

19" Monitors:
Once again, I choose Sony's FD Trinitron monitors with .24mm aperture grille pitch. These models include HMD-A440, CPD-E440, and CPD-G410R.
Other monitors that use the same tube as the Sony monitors above, but for a lower cost, include the Philips 109P40, IBM P97, and probably others..
Also worth considering are the NEC/Mitsubishi Diamond Pro 930SB and FP912SB which also have a .24mm aperture grille pitch and are similar to Sony's but use NEC's own tube.

21"And Larger Monitors:
Sony's GDM-F520 is a 21" Trinitron monitor with an amzaing .22mm aperture grille pitch. This is by far the best monitor you can get. However, the cost is prohibitively high (about $1,500) - twice the cost of other "good" 21" monitors. It has the sharpest image available though, and you can tell the difference.
Sony's CPD-G520 and CPD-E540 are 21" monitors with a .24 mm dot pitch throughout (not variable).
A good alternative to the Sonys is the NEC/Mitsubishi 22" Diamond Pro 2040U is a "Diamondtron" monitor (Mistubishi's version of Trinitron). The dot pitch is slightly higher at .24.
There are a couple other good options that use the same tube that's in the Sony CPD-G520 (just a different case and controls). These include the HP P1130, IBM P260, Compaq P110, IBM P275, Nokia 445Pro, and the CTX PR1400F (which comes with a USB Hub).
The Viewsonic P815 is a good choice if you prefer shadow mask monitors. This display has a .25mm dot pitch for a crisp display along with a USB hub.
Another good shadow mask choice is the Iiyama Vision Master 504 (model # S104MT). This 21" monitor also has a crisp .25mm dot pitch.