taste it. there are no known pathogens that can live in beer. if it tastes ok, its probably ok.
contamination usually looks obvious: clumps of fuzzy mold, weird 'strings' of slimy stuff (sorta like egg drop soup).
the fact it doesn't smell funny is a good sign its ok and that's just some floating yeast/trub, possibly covered in tiny CO2 bubbles lending a whitish appearance.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10