There’s MSP430ware which you can use. It is a collection of library functions for operating the various peripherals and the clock system.
Also, for 2x family devices, there is GRACE. It makes configuration easy and provides some base stubs for low-level processes.
Then there are several multitasking OS implementations (RTOS, CONTIKI etc.). Since they need to be ported for each target MSP, not all MSPs are supported. Also, they require quite some flash and ram space, so they won’t be too useful on the smaller MSPs.