I don't know how well-known this thing is, as I've been
drawing up a board with SMT parts, I've been using
a free calculator on IPC's website. The page is at
http://search.ipc.org/SM782/default.asp (it does require
registration, but the allow you to log in thereafter
with only your email address).

There are pull-down menus to select the package you will
be using, which may be specified three different ways. It
then will give you a web page with complete specifications
for the placement and dimensions for the SMT pads as well
as exactly how the device leads will be soldered to the
pads: Minimum toe & heel and side fillets are given.
This is nice because the part vendors usually just give
you the package dimensions and leave it as an exercise
for the customer to figure out how big to make the pads.

In particular I found it useful for figuring out whether I
have the correct package in Eagle, and for cross-checking
their drawings. (Eagle's IPC libraries seem to be OK
and AFAICT match IPC's specs down to the micron, but
the packages in smd-ic.lbr are very sloppy and some are
almost unusable.)

--Bob

--
============================================================
Bob Drzyzgula                             It's not a problem
bob@drzyzgula.org                until something bad happens
============================================================