They can be more common than you think, in other leagues:
Peter Schmeichel
The great Dane has a history of scoring goals and had his most prolific season in 1985 when he scored a remarkable six goals in 28 games for Hvidovre. After a move to Brondby, he then scored two more for the Danish giants in 1987.
With Manchester United, he memorably popped up in the penalty area to score an equaliser from a corner in an UEFA Cup tie against Rotor Volgograd in 1996 though United went out on the away goal rule.
The final goal of Schmeichel's career came in October 2001 when he scored from another corner for Aston Villa in their 3-2 defeat away at Everton.
Pat Jennings
Possibly the most famous goalkeeper's goal of all time was Pat Jennings' amazing strike in the 1967 Charity Shield.
Playing for Tottenham against Manchester United, the Northern Irishman punted a long clearance upfield and when the ball was caught by a strong wind, the ball flew over a rather embarrassed Alex Stepney.
Hans-Jorg Butt
Remarkably, German international 'keeper Hans-Jorg Butt scored 19 times for SV Hamburg between 1997 and 2001.
The best season came in 1999/00 when he hit the back of the net nine times and was the club's top goalscorer.The season before had seen Butt get seven goals, with only Tony Yeboah outscoring him.
Jose Luis Chilavert
The most prolific goalkeeper in history has scored over 50 goals at all levels, including one hat-trick. Between 1993 and 1997, he scored 17 league goals for Velez Sarsfield and was the free-kick and penalty-kick taker for the Colombian national side.
http://www.thefa.com/Features/EnglishDomestic/Postings/2003/09/66983.htm