Of course, W. does have a $200M war chest, a good part coming from corporate donors, as the liberal media reports incessantly. But a lot of Republican money does come from small donors.
Anyway, progressive causes appeal to people with disposable income. They want to use their money to change the world. The analog of moveon.org for conservatives is more of a reactionary cause. How many wealthy conservatives with disposable income become energized to combat these nutty progressive causes? Something like school choice would be a worthy cause, but I guess it doesn't appeal in the same way to someone who has money and wants to use it to gratify their messiah complex.