I have a 13" black macbook and am looking to buy an external screen display for my it. Any suggestions? What size can I go up to? Was thinking about a dell, seem cheap, good quality, opinions?

Practically any monitor will do you - the max output resolution of the MacBook's graphics card is 2048x1536.
Extended desktop and video mirroring: Simultaneously supports full native resolution on the built-in display and up to 1920 by 1200 pixels on an external display, both at millions of colors
Intel® Graphics Media Accelerator 950 Graphics Core - 2048x1536 at 75 Hz maximum resolution
http://www.intel.com/products/chipsets/gma950/
That's off Intel's website - but the Mac driver is different as some say, so dunno who's right.
I would recommend looking for an older 20" ACD if you don't want to put up the money for a new one. That's what I ended up with after first buying a Samsung 206bw, and I'm much happier with it both in terms of looks and quality.
Did you end up buying it through the Apple refurbished store?
I'm in the market for a new display and was looking at a couple of 20" Samsung monitors, but after your post, I may consider the refurb route if the price difference isn't TOO much.
The 206BW was one of the ones I was looking at (205BW the other) - what didn't you like about the quality?
Thanks!
Yes, the 206BW is a 6Bit Display whereas the ACD is an 8-Bit with a more finely tuned Color Lookup Table which is HUGELY important for interfacing the monitor with the video card and Mac OS via a ColorSync Profile -- this LUT is basically coded as a very complex algorithm that describes each pixel of color via Colorsync.
So many underestimate the "out of the box" use of this. So many tout "end-user calibration" but this is a whole other can of worms -- it presumes so many things from lighting to accuracy of the calibrator to quality of the profile software.
I recently switched from M$ and purchased a macbook. After reading this and other forums, I decided to get an ACD 23". I appreciate that other monitors are now significantly cheaper and have height and pivot options. However, I must say that the Apple display is a fine piece of kit, and I am very very happy with the clarity of the screen. No dead pixcels, and the stand height is fine.
If you spend an hour or so on this forum you will find some in depth analysis from people who clearly have detailed knowledge of screen technology. At the end of the day you have to live with the thing and be happy. I certainly have no regrets whatsoever about the ACD. Best of luck.