What are the best easy online games for adults?

I'm looking for online games for my mother to play, she is semi computer-illiterate so they need to be easy but fun and not designed for 5 year olds. High preference for games using mouse only, but easy keyboard games are good too. To give you an idea for what she is looking for, she really enjoys Peggle, but the free online version only has about 5 levels and the pinging noises are driving me up the wall! Thanks for your suggestions.