t-molding slot cutter

[Brian74]

Where is the best place to buy one?

[Vigo]

Harbor Freight if you got one near you. Otherwise, amazon or some online store is fine.

[RandyT]

If you are only going to use it once or twice, the cheap Harbor Freight ones are fine.  They tend to be flimsy and dull quickly, and once they loose their edge, it can even become a safety issue.  If you want to keep one in your tool box to use whenever you might need it down the road, I recommend getting a quality bit.  T-molding slots can be tricky enough without fighting additional challenges presented by low quality cutters.  

[Unstupid]

Woodcraft if you have one near you!  CMT Orange bits are awesome!  This is the one I use but it has a 1/2 shank.  They make a 1/4" shank version as well if that's all your router can do.

[kahlid74]

I use the ones from T-Molding of Whiteside brand and they work fantastic.  I would recommend them every day of the week.

[GregD]

Here is an ebay link to the one I purchased.  It is a Porter Cable and good quality.  $10 shipped cannot be beat.  Make sure your router can handle a 1/2 shank.  I wouldn't spin a slot cutter on a 1'4" shank.
http://www.ebay.com/itm/Porter-Cable-1-16-Slot-Cutter-w-1-2-Shank-Arbor-Router-/140442782832

[Brian74]

Far as I know mine is a 1/4.