Just found a great new page, Spending Wisely, that I plan to peruse in greater depth when I have a bit more time. I already found a great article about how much money we should be saving each month. In the article, the author talks about the notion that people should be putting 5% (or so) away per month and how that figure is not indicative of what could be happening. Her main point is that we should be putting away propotionately more money (not just actually more money, but a higher percentage) as our income levels rise.
I completely agree with her sentiment. Even in grad school, I intend to put money away into savings each month. I'll actually be making more in graduate school than I've ever made before, since I've never had a full-time year round job (then again, I have higher expenses too, but I don't intend to spend all the money that I'll be making each month). Even last summer, when I was living on my own and taking care of all my expenses, I managed to put away almost 50% of my paycheck each month. While I expect the percentage will be a bit lower here (mostly due to higher rent), I anticipate putting away quite a chunk.
Just because you make a certain amount of money doesn't mean that you should allow yourself to spend all that money each month. Saving is just about living within your means; it's about living below your means and continuing to do so even as your means increase.