As a user of Rutherford's MPSGE, I have written several introductory pieces, which some people find useful.

Moving from Static to Dynamic General Equilibrium Economic Models
A Spanish version of the paper kindly translated by Juan Carlos Segura can be found here (PDF format)

From an Input-Output Table to a General Equilibrium Model
A Russian version of the paper can be found here (PDF format)

The GTAPinGAMS Package

The EPPA model documentation (in PDF format)

For other information about computable general equilibrium modeling with MPSGE, visit Tom Rutherford's homepage at http://www.mpsge.org