I was just giving my mother's mobile for repair at my local store and saw the owner stocking parts for them. I saw him stocking cheap (I mean really cheap) LCD (coloured and black & white). I was wondering where I can learn to use them in my circuits.
Google seems to be the best bet AFAIK. The modules vary wildly. There are types that resemble a TV with horizontal and vertical sync and pixels, ones with smart controllers (even SPI, as in a 3310 IIRC) and probably some had bare segments. Most probably don't have easily published specs.
Another thing you'll have to worry about is the connector types. Many cellphone parts have incredibly tight pitch components.
It all depends on the controller. Some are well supported in the embedded world, others have their datasheets hidden away for OEMs only, are unpublished, or have completely unreadable barely-English text.
I'd stick with the LPC2148 [Sparkfun], which uses the Epson S1D15G10 or Philips PCF8833 controller. C code for AVRs, PICs, and ARMs, Arduino sketches, Forth implementations, Linux drivers, etc. are all available.
A friend of mine did a teardown of an LCD that he purchased for 0.50USD from Electronic Goldmine -- http://tim.cexx.org/?page_id=342
It is quite detailed so even if you don't use that particular screen you may be able to follow the steps to interface other screens.
I've used an old Nokia LCD display (GLCD5110) and it's quite simple to use as it uses SPI to communicate with the CPU (LPC2103 in my case).
So it uses basically the MOSI, CLK, CE (Chip Enable) and RST pins and you can send commands and data to the LCD through the SPI interface.
I bought it here: http://www.robotshop.com/inex-graphic-lcd-5110.html
I discovered this the other day it might be of some use for pin layouts.