Found this nice code plugin someone wrote. I'm testing it a little in some code segments below.

This is not as fancy as what the code display wordpress can do. As you cut&paste this code you will also copy the line numbers.

But heh, we all know vi. With the following search-and-replace you can remove them again:

:%s/^[0-9]* //

Some examples

1 int main(int c) {
2     printf("This is nice");
3     exit(1);
4 }

1 int main(int c) {
2     printf("This is nice");
3     exit(1);
4 }