PharMingen has excellent antibodies, Serotec, Bachem, others.  Many mouse
markers work best with frozen sections, some have success with paraffin,
and if you have to cut thicker sections, be careful, background may become
a problem. You can buy some antibodies directly conjugated to fluorescent
markers, or buy biotinylated and come back with Strepavidin-fluorescent
labels, our favorite trick for Immunofluorescent work  on tissue sections
We use the Alexa 488, a FITC equivalent or Alexa 546 a TRITC aka rhodamine
equivalent because they are brighter, and more stable in UV light with very
low concentrations.  
These come from Molecular Probes, who are excellent in helping you with
your fluorescent confocal needs and other IFA applications. 

Gayle Callis