ES File Explorer File Manager
If you passed on ES File Explorer File Manager in the past, take another look -- it has improved in leaps and bounds over the last year or so. It now can browse files on LAN-based SMB servers as well as cloud services including Amazon S3, Dropbox, Skydrive, Google Drive, Ubuntu One, Yandex, SugarSync, and Box. It supports Bluetooth and FTP, and it will open Zip archives, tarballs, and other compressed files. It does a great job of helping you find stuff on your device, and does a pretty good job of displaying images, video, and PDFs too.
Compatibility: Android 1.6 and up