An actions log can be used to record activity that needs to take place following on from key meetings, or to help you keep a log of what you need to do/when.
A decisions log is similar to an actions log, it is a record of why you made certain decisions for your project – it can help save you time trawling through emails to find when/where you made a decision/changed direction etc…
These tools are also useful if you need to handover a project or include a new team member, as a quick way to get up to speed.