freeware / open source

package of many tools

• SWFTools
• Flagstone's tools

decompilers

• flare / flasm
• "How to create a simple SWF decompiler with the SwfDotNet library"
• Google Code project

extractors

• swf extractor
• FlashProbe.com (web-based tool)

creators

• SwfDotNet
• Ming

payware

decompilers

• Sothink SWF Decompiler (video overview) — available on bit torrent
• Action Script Viewer
• moar

other lists like this

• osflash.org
• flashsec.org