Here's another vote for Apple's refurbs--the only difference is that the box it comes in isn't as pretty and you save money.
To those recommending Samsung and HP displays, keep in mind that most of the displays on the market use less-color-accurate TN panels rather than the high-end IPS of the 24" Apple screen. There are times when TN is actually preferable (faster response time for gaming), and depending on your eyes and use you may not care, but the point is the price premium exists for a reason.
To my knowledge the only IPS monitor Samsung makes is the 305T, a 30" monster that costs around $1250 (I have seen refrubs as low as $850).
HP has the LP2475, which is much more comparable at 24", though it uses a CFL rather than LED backlight. It lists for $650 and has a street price a little under $600. Factoring in the LED, much sexier design, and camera, Apple's higher price is reasonably competitive I think.
HP also makes the DreamColor LP2480zx, a 24" IPS with an LED backlight, and with a 10-bit panel is probably better than the Apple display in terms of color reproduction. It also has a list price of $2000, and the street price isn't all that much lower.
Not bashing Samsung or HP monitors, just pointing out that Apple's price isn't arbitrarily high.