Update: These instructions are no longer needed! The screen reportedly works with Snow Leopard 10.6.2 without any additional software. (Thanks to Mr Sitek for this information.)
I recently got a Samsung SyncMaster 2343NW to be used as an external display for my aluminium MacBook (late 2008). I had some problems with the resolution, but I managed to solve them.
I connected the display using VGA (with Mini DisplayPort to VGA adapter) as 2343NW does not have DVI port. At first, OS X wouldn't let me use the display's native resolution, 2048x1152. The display settings in system preferences offered 1920x1080 as the maximum resolution.
I found a program called SwitchResX, which lets you enable more resolutions. After some trial and error, I discovered the following settings. Go to SwitchResX Control Panel, add a custom resolution with these settings and reboot. Poof, the display magically works. Note: while the refresh rate is 55 Hz in the settings, the display actually runs at 60 Hz.
The contrast is so bad it annoys me. Which means it actually is somewhat bad. For example in iTunes, the song lists are striped with blue and white, but on this screen you can't actually tell the colors from each other. Oh well, it's a cheap one, and I like the 16:9 widescreen format.