Creating an array of LEDs to make a display

I want to try to make an array of LEDs to output an image which I will generate on a computer (I suspect I will use processing for this but this is not important).

Is this possible using an arduino. I think that I will need to have an array of at least 24 x 24 LEDs. The image will need to change but it does not need to have a superfast refresh rate but it will need to be fairly responsive.

Any ideas?

There have been a number of projects on these pages using Maxim 8x8 LED matrix controller chips. These have a 4 pin serial interface and I suspect can be daisychained so you could use 9 of them to get your 24x24. Searching the forum for "matrix" should point you at some.