  We perform a combined fit to angular power spectra of unresolved infrared
(IR) point sources from the Planck satellite (at 217, 353, 545 and 857 GHz,
over angular scales 100 < l < 2200), the Balloon-borne Large-Aperture
Submillimeter Telescope (BLAST; 250, 350 and 500 um; 1000 < l < 9000), and from
correlating BLAST and Atacama Cosmology Telescope (ACT; 148 and 218 GHz) maps.
We find that the clustered power over the range of angular scales and
frequencies considered is well fit by a simple power law of the form C_l
\propto l^-n with n = 1.25 +/- 0.06. While the IR sources are understood to lie
at a range of redshifts, with a variety of dust properties, we find that the
frequency dependence of the clustering power can be described by the square of
a modified blackbody, nu^beta B(nu,T_eff), with a single emissivity index beta
= 2.20 +/- 0.07 and effective temperature T_eff = 9.7 K. Our predictions for
the clustering amplitude are consistent with existing ACT and South Pole
Telescope results at around 150 and 220 GHz, as is our prediction for the
effective dust spectral index, which we find to be alpha_150-220 = 3.68 +/-
0.07 between 150 and 220 GHz. Our constraints on the clustering shape and
frequency dependence can be used to model the IR clustering as a contaminant in
Cosmic Microwave Background anisotropy measurements. The combined Planck and
BLAST data also rule out a linear bias clustering model.
