There is no official bitcoin symbol as of December 2010, however the BTC abbreviation is the most universally accepted form.
There is a discussion over which unicode symbol might be the best suited for bitcoin.
It has lead to the following options:
- Pro: Gives a currency-like look (it the symbol for an existing currency, the Thai Baht, but other currency symbols often get reused, like the $), Displayed correctly on all known OSes
- Cons: It is already a currency, and might confuse people
- Cons: Do not even think about it
- Ⓑ ⓑ
- Cons: Do not display properly for everyone