You've gotten great responses already so I don't have anything to add. But I thought I'd let you and other pumping moms know about a great resource - there is a yahoo group called PUMPMOMS.
It has been an amazing resource, with lots of great information from and for women who exclusively pump, who pump at work, or who pump it occasionally. With my first son, I searched everywhere for resources about how to increase supply and found very little. With my second, I've found lots of great tips just from reading my daily digests from this list.
Although there are a lot of messages, they stay on topic and responses are very helpful - either practical (what's the best way to pump hand-free?), technical (how do differnt herbs work to support supply), or emotional (how do I decide when to stop pumping).
In addition to the tips, I've found it is really helpful to hear the stories of women doing the same thing as me.