Here's a very good article about the dangers of static electricity when fueling aircraft. There are some risks here discussed that I had never heard, so I found the article very useful.
From the article: Always remember these key points:
Also, it seems using a chamois to filter the fuel can greatly increase static electricity buildup.
Here is a link to the PDF: http://www.caa.govt.nz/fulltext/vector/vector_05_5_sept_oct%2005.pdf