Hate on display. The Anti-Defamation League has a visual database of symbols devised or co-opted by neo-Nazis and supremacist groups worldwide, as well as numbers and acronyms with racist connotations. Although most of us know what 88 means, there's also info about others such as the communist-separatist American Front and the Five Percenters. More neo-Nazi flags here; flags and badges here.
Please remember: while racism is always immoral, symbols themselves can have several meanings. [MetaFilter]
To me, being aware of this is very important, the symbolic content of our everyday life is ever increasing, and the more there is the more overlapping meanings there are. We need to be careful to use symbols that represent our intent, or appropriate symbols for new uses as a form of cultural resistance to institutionalized and disseminated forms of hatred.