CQPolitics.com has put out an updated version of its handy-dandy chart (in PDF format) of Senators up for re-election in 2008, including each Senator's Q1 take and post-Q1 cash-on-hand.
What strikes me most as I review the chart, and what really puts in perspective John Warner's $500 Q1 take, is this: Senator Wayne Allard of Colorado, who announced in mid-January that he would retire at the end of this term, raised over $12,000 in Q1. Allard has no more Senate campaigning to do for himself ever again, but still took in over $12K.
It just demonstrates what a concerted effort it takes for a long-time incumbent Senator to not take in at least a few thousand dollars just for holding office. You have to actively turn away contributions. So, there's some perspective - take from it what you will.