I have visited the Kingdom of Bahrain on several occasions. The last time I was there (December, 2006) I actually did more than eat out and drink cocktails with friends.
There are many sites of interest in Bahrain. I have included pictures of a few. I went horseback riding in Sitra on Christmas day. We drove out to the Tree of Life and also went and explored the old Portuguese Fort. The best way to get around in Bahrain is to hire a driver like our ship's crew did, take a taxi, or know someone that lives locally.
All the locals seem to know where everything is... most speak some English. I do not recommend renting a car because as in most third world countries... there don't seem to be any rules about driving there... Unless of course you happen to get caught.
The tree of life was pretty boring. There is no information on it at the site. Everything I found out about it was from friends who had been there or from Google. It is a 400 year old mesquite tree with graffiti all over it. It is growing in the middle of the desert all by itself with seemingly no water supply.
The Portuguese Fort was much more interesting. It has obviously been reconstructed very recently. However, like the tree, there was no information on it at the site. Evidently the Portuguese built it (in the 14th century) on top of a fort built by an earlier civilization.
There is also a very good National Museum to visit. It gives some history on the old forts on the island and on other local sites of interest.
There are several clubs and bars in Bahrain. Be aware that most of these are frequented by prostitutes.