I've got a Dell 24" (1900 x 1200) monitor running alongside my 24" iMac (also at 1900 x 1200). Yes you need the short (4" long) mini-DVI to DVI adapter.
I've got vmWare Fusion running full-screen on my Dell monitor with a virtual snapshot of my old PC (XP Pro, SP2) running perfectly on it.
So I'm not using the slow, noisy, old Dell box anymore.
Instead I've got a zippy, near silent, iMac running OS X on the main display and my old XP environment on the second monitor (at about 5x the speed of the old XP box).
Couldn't be happier. Making the transition from PC to Mac will be a gradual one as I slowly find/migrate to Mac equivalents of my old PC favourites.
Good luck!
.../j