Classical ones are on the Quine page (which is apparently not maintained anymore).

The shortest non-empty non-cheating one I know is (ends with two newlines)

print<< x2,v10
print<< x2,v10
[download]

Another that uses perl's various quoting operators to avoid having to escape stuff dynamically is (no newline)

$a=q(;print"\$a=q($a)$a");print"\$a=q($a)$a"
[download]

Update: see Short quines.