SpeedDisk 2.0 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The application lies within System Tools, more precisely System Optimization. The actual developer of this free software for Mac is MacDaddy.
From the developer:
SpeedDisk is a hard drive cleaner for your Mac. The application scans your computer for useless files like catches, logs, mail downloads, etc., and offers to remove them in order to regain valuable free space. In addition, it helps you restore your speed and get your privacy back.
You may want to check out more Mac applications, such as Peek-a-Boo, DiskFire or DisplayConfigX, which might be related to SpeedDisk.