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