is it possible to partition the SD card and install 2 different OS on it? Rather than installing another OS onto a seperate SD card. I was just wondering as I'd like to be able to have openelec + XBMC as one operating system but as this OS doesn't have a web browser I'd like to have a seperate OS on the same SD card that does have an integrated browser such as Raspbian for example. Which I can choose between the two OS depending on whether I wanna browse the web or use the XBMC.
Take a look at BerryBoot. It allows you to put multiple operating systems on an SD card and select between them at boot.
They have a good walkthrough on how to install BerryBoot and your operating systems here: BerryBoot Walkthrough.