what type of lcd?? for graphics LCD you could find some LCD Graphics with SPI or I2C controller from mobile phone like Nokia 3310 display it used Phillips PCF8544 or you could integrate microcontroller on it to provide interface that you want. Maxim also provide some I2C Key Matrix scaner I think I seen it befor
You could use a Philips PCF8574 Remote 8-bit I/O expander for I2C-bus to connect between the MCU and a standard Alphanumeric LCD display in "four bit" mode.
You could also use a Philips PCF8574 for connecting the matrix keyboard.
To use an i2c I/O expander is a good idea, especially if you have eeprom on the same bus or other i2c device. If you are using x51 micro at www.wickenhaeuser.com for example on their compiler they have an apllication note and a library on how to control an LCD by PCF8574. If you have a slow connection and don't wont to downlowd the full compiler i can send the pdf to you. In september 2003 number of Elektor there is an article about the subject but i don't have the magazine.
If you are looking to get a keyboard to output i2c then take a look here:
**broken link removed**
There is info there about the keyboard as well as code for the z80 microprocessor that will control a keyboard. There is another section on the same website that gives code for a communication using a PIC microcontroller. You may be able to use some of the PIC Code to accomplish what you are trying to do. Notice though that the code is not I2C as is. It will need some refinement. The explanation of the keyboard is pretty thorough.
PCF2116 from Philips is a family of i2c LCD driver. There is the application AN0149 from Zilog (www.zilog.com ) on how to interface this driver in C; also a project with ATMEL on http://www.woe.onlinehome.de/e_lcd.htm