  [Abridged]
  Simulations and observations of the microwave sky are of great importance for
understanding the Universe that we reside in. Specifically, knowledge of the
CMB and its foregrounds - including the SZ effect from clusters of galaxies and
radio point sources - tell us about the Universe on its very largest scales,
and also what the Universe is made of.
  We describe the creation of software to carry out large numbers of virtual
sky simulations. The simulations include the CMB, SZ effect and point sources,
and are designed to examine the effects of point sources and the SZ effect on
present and recent observations of the CMB. Utilizing sets of 1,000
simulations, we find that the power spectrum resulting from the SZ effect is
expected to have a larger standard deviation by a factor of 3 than would be
expected from purely Gaussian realizations, and is significantly skewed towards
increased values for the power spectrum. The effects of the clustering of
galaxy clusters, residual point sources and uncertainties in the gas physics
are also investigated, as are the implications for the excess power measured in
the CMB power spectrum by the CBI and BIMA.
  We carry out end-to-end simulations for OCRA-p observations of point sources.
The introduction of simulated 1/ f noise significantly reduces the predicted
ability of the instruments to observe weak sources by measuring the sources for
long periods of time.
  The OCRA-p receiver has been used to observe point sources in the VSA fields
so that they can be subtracted from observations of the CMB power spectrum. We
find that these point sources are split between steep and flat spectrum
sources. We have also observed 550 CRATES flat spectrum radio sources, which
will be useful for comparison to Planck satellite observations. Finally, the
assembly and commissioning of the OCRA-F receiver is outlined.
  [Abridged]
