If you think you've read this before it's because I just posted it as a comment on Amabelle's blog (about how people think we Asians all look alike) but thought it deserved a full post on my own blog.
What used to REALLY boil my blood was when I was at a grocery checkout stand behind some other Asian people I didn't know. The cashier would finish with their purchase, skip me and help the white person behind me. I'm like "what about me?" pointing at my food. And they'd reply "oh I thought you were with them" motioning to the Asians walking away with their groceries. This has happened far more times than I can count. The only thing that makes me feel better is when they look embarrassed, but most of the time they don't.