If don’t have access to a full version of one of the major MSI software packaging tools, you can still get far by using free software. They don’t have all functionality in a slick and easy user interface, but are quite good. 🙂
InstEd, is a free MSI editor for professionals. If you have used ORCA before, you will find this to be better and faster. Check out the feature list.
Advanced Installer can make simple MSI packages from scratch, and as long as you stick to the Simple template, it is free. If you need to do custom actions, signing, file associations, services etc. then you’ll have to buy a license.
AppDeploy Repackager from Dell KACE are a simple repacking tool. Just start it up, make a snapshot, do whatever you would like, install, configure, copy or edit, and then make a new system wide scan and you’ll have the changes in a MSI package. Not so useful if you’ll need to do customization afterwards.
EDIT: 2012.05.26: New download LINK
EDIT: 2012.05.09: Universal Extractor from LegRoom allow you to extract files from virtually any type of archive, regardless of source, file format, compression method, etc. (MSI, EXE, InstallShield, Inno, VISE, WISE etc.) It is last updated back in 2010 so if anyone have a tip for a better utility, please comment below.
InstallSite has a good list of many of the Windows Installer Authoring Tools available for commercial as well as free ware
EDIT: 2012.05.28: Under the Software Installer Unpackers Section on the Tweaks and Fixes page at www.JSWare.net you can find information about almost every Software Installer Unpackers.