STM32F2 build environment
You would need to install


Eclipse IDE for C/C++ Developers
CodeSourcery Lite (ARM processors EABI Release) - a GCC toolchain for ARM
GNU ARM Plugin for Eclipse - simplifies GCC configuration


I have a project with Eclipse Juno + CodeSourcery Lite + J-link GDB + SMTM32F4/F2 + FreeRTOS 7.3 + lwIP 1.4.1 ( PHY is KSZ8051). So if you have any specific troubles just let me know.

There is also CooCox CoIDE. It's Eclipse based and it's already preconfigured and works with J-link and ST-Link. For me the only downside was that it doesn't support C++ but only C.