Where are some lists of system calls on UNIX?
This wasn't my original question, but thanks anyway :)
man 2 syscalls
Aside from that, you can look in /usr/include/sys/syscall.h (which on my system merely #includes /usr/include/bits/syscall.h). That's generated at libc build time from kernel syscall list.
You can also grep the Linux kernel source for SYSCALL_DEFINE. (I'm not a BSD expert, but I think the equivalent in FreeBSD is SYSCALL_MODULE)