Suspicious Package allows you to preview the contents of a standard Apple installer package without launching the Installer. You can click individual folder names to see their contents, or click the Show Contents button to see all content at once.
QuickLook plugin allowing previewing of a wide array of compressed file types. Currently supports: ZIP, TAR, GZip, BZip2, ARJ, LZH, ISO, CHM, CAB, CPIO, RAR, 7-Zip, DEB, RPM, StuffIt's SIT, DiskDoubler, BinHex, and MacBinary. Version 1.1 brings additional view options, collapsible folders, and many other features.