I know very little of the Fathers: I freely admit my ignorance. I just want to say that because I don't want to give anyone the impression that I think I'm some kind of "patristics scholar" just because I quote them a lot. I think we need to follow them (that they are as close to an infallible interpreter of Scripture as we can get), and so I quote them a lot. I don't, however, mean to ever say that I "understand the mind of the Fathers" as though I'm some advanced theologian. I freely admit that I'm the opposite; I'm an ignorant sinner. With that in mind, then, I'd like to list some of the sources that I use to find patristic references each week:
Textweek - I get probably around 60% of the quotes from this source.
Christian Classics Ethereal Library - Place I normally link to when I quote the Fathers. Good selection of Saints and also more contemporary writers. (There's even a Russian section.)
(I have a number of links to other similar pages here.) Past these sources, I just look up stuff in books that I have (in topical and scriptural indexes), and I also use the Harmony of the Gospels feature in my Thompson Chain-Reference Bible to find other possible Gospel passages that might lead to patristic references. So... the cat is out of the bag! 