There are tons of various development boards around the internet. If you are looking for one - might be this one will fit your needs. It is featured with

• ATMega32 MCU clocked at 16MHz;
• RS232;
• RS485;
• I2C EEPROM (64KBytes);
• 4-way Piano Switch;
• Reset and some LEDs;
• 2 x 40 pin DIL breakout connectors.

Board is 100×75mm size with tracks on both sides. Probably it is best to send Gerber files to your nearest PCB manufacturer and get professionally looking PCB.