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Scanning Hall probe microscopy (SHM) is an important new magnetic imaging technique that allows direct spatial measurement of magnetic structures with high magnetic sensitivity and spatial resolution. This combination of features has allowed us to study aspect of two distinct superconducting systems that would not be possible using other methods. An array of isolated type I superconducting rings at an applied flux of $\phi\sb0/2$ is expected to behave like a two dimensional random field Ising antiferromagnet, with the quantized magnetic-moments of the rings analogous to Ising spins. SQUID magnetometry confirms the antiferromagnetic interaction between rings, while the SHM directly images specific configurations of spins. We find significant antiferromagnetic nearest-neighbor correlations, but no evidence for any long-range ordering. We attribute this to a significant degree of disorder in the system related to small fluctuations in the areas of the rings. Spatial images from the SHM give new insights into the problem of how magnetic fields penetrate the interior of type II superconductors. We observe vortices driven into superconducting samples with two different geometries by ramping an external magnetic field. In a 50 $\mu$m diameter niobium disk, images show remarkable correlated regions where the field has changed by a value different from the external field increment. We identify these regions as resulting from avalanches of correlated bundles of magnetic flux. The flux contained in these bundles decreases at higher magnetic fields and temperatures, while the diameter of the bundles is independent of field and temperature. Field penetration into a 100-$\mu$m-wide strip of niobium is seen to occur in the form of small ($\sim$10 $\mu$m wide) dendritic fingers which grow smoothly as the field is increased. This suggests a growth mechanism of the flux front possibly mediated by the long-range interactions between mesoscopic flux-containing regions. We have also observed vortex motion due to transport currents in these niobium strips. When the critical current is exceeded, certain regions of the sample exhibit field fluctuations on time scales orders of magnitude longer than the travel times of single vortices. Such fluctuations indicate patterns of possible channels of irregular vortex motion that become more uniform with increasing current.