What's your good pdf reader of choice? And do you use any software to organize your collection, or just the filesystem?
I recently went back to school and started using Zotero again. Reading and annotating books and papers on iPad, and then having access to all of my notes when writing on desktop is such a simple but amazing feature.
My PDF are managed by Calibre, but I export various subsets to the file system, so I can find them easily (on the network).