My sun roof decided to leak on me today (literally).  When I got home
and the rain stopped, I rolled the sunroof back and saw standing water
in the grooves.  Figuring the drains were blocked, I took a look and
couldn't see anything.  Scratching my head as to what to do, I decided
to snake something down through the drain until it cleared the clog.  
Several tools were attempted without success, but a heavy duty mountain
bike brake cable worked great- the right combination of flexibility and
stiffness.

Hopefully the raindrops will no longer be falling on my head!