A list of working (until proven broken!) Arduino functions:
millis();
microSeconds(); //Good luck with this on a multitasking operating system!
delay();
//PROGMEM related functions. Be careful with this though, many pitfalls may exist
strcpy_P();
strlen_P();
pgm_read_byte();
pgm_read_word();
//LiquidCrystal library. Will work on write(char), print(int) and print(float)
begin();
clear();
print(char*);
print(char);
//Will work to port phi_prompt user interface library and its physical layer phi_interfaces to PC