The FREE IPC-7351B LP Calculator is a fantastic time saver. It is a land pattern calculator based on the IPC-7351B SMT land pattern standard that allows you to define your own CAD land patterns and offers seamless compatibility with the freely-distributed library documentation.
The Institute of Printed Circuits (IPC) has standards for “land patterns” (as they call pad shapes). You can download a free calculator from pcbmatrix.com that lets you generate IPC standard land patterns for any component. It still seems ridiculous, though, that every designer has to reinvent this wheel. There should have been a standard symbol and footprint file format invented a long time ago, with every component manufacturer providing downloadable libraries for their parts. You can download SPICE models from manufacturers, but have to do everything else yourself, or pay big $$$ for quality commercial libraries.