supports MSP430 and some TI ARM chips (and apparently the C2000 DSP chip as well!) (various TI "LaunchPad" Eval boards.)MPIDE
supports PIC32 chips and (in particular) the ChipKit boards.TeensyDuino
is an Arduino addon that supports a Freescale Cortex M4 board ("Teensy3")
I don't know of any attempts to support large number of different chips in one IDE; you'll generally need a separate (very similar looking) IDE for each family of boards. (actually, I think mpide and teensyduino can still build AVR code.)
Library support can be skimpy; a lot of the libraries are meant to deal with on-chip peripherals (say, I2C) in a way that is very specific to a particular chip, rather than in a way that would make it "generic" enough to use on many different chips.