Hallochen aus Schweden,
you would be surprised about what the Arduino IDE can actually do 
As a matter of fact, last weekend in London we had Nick Zambetti's library for dot-matrix LEDs ported to Arduino working like a charm.
You can write your own C libraries and by just adding them to the folder /lib/targets/arduino, they will become part of your project if you happen to use them. (I haven't checked, but I guess that it would also work fine to have the libraries in the same folder as your actual arduino code).
Libraries are only compiled and included in the code if you happen to call any of their functions, otherwise they take no space in memory.
/David