I have a 5GB database and a 20GB transaction log (SQL Server 2005). Not sure why it is so large or what happened to make it that large, it used to be around 1/2 the size of
If you have a lot of transactional behavior, it's not uncommon at all. However, you probably should investigate means of making it smaller. There are quite a few options for this, but without knowing your recovery model, I could never presume to make a recommendation. Start with this MSDN link, this knowledge base article, then move from there. Carefully. :)