Steven M. Massey, a former Digidesign and Trillium Lane Labs employee has released several plug-ins for free. That is right FREE!.
Here is the link to some "Utility based Plug-ins".
These include metering, backing up and other various plug-ins not necessarily audio based.
If you are after some more "Audio" based plug-ins then have a look at the Massey High end plug-ins. Here you can download demo versions of often used plug-ins. As the web page state, you have "unlimited usage period and introduces no mutes or beeps to the audio. Use it as long as you like."
Please read all disclaimers though in regards to the use of these plug-ins.