  We present an analysis of the mid-infrared (MIR) and optical properties of
type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR
color-redshift relation is characterized to z=3, with predictions to z=7. We
demonstrate how combining MIR and optical colors can yield even more efficient
selection of active galactic nuclei (AGN) than MIR or optical colors alone.
Composite spectral energy distributions (SEDs) are constructed for 259 quasars
with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by
near-IR, GALEX, VLA and ROSAT data where available. We discuss how the spectral
diversity of quasars influences the determination of bolometric luminosities
and accretion rates; assuming the mean SED can lead to errors as large as a
factor of 2 for individual quasars. Finally, we show that careful consideration
of the shape of the mean quasar SED and its redshift dependence leads to a
lower estimate of the fraction of reddened/obscured AGNs missed by optical
surveys as compared to estimates derived from a single mean MIR to optical flux
ratio.
