What are some alternatives?
When comparing SpaceSniffer and DaisyDisk, you can also consider the following products
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
WizTree - WizTree quickly finds the files and folders using the most space on your hard drive. It scans the MFT (Master File Table) instead of crawling the entire disk which makes it very fast.
Baobab - Distributor of workload automation, financial statement reporting, data access, IT Asset Management and Service Desk software solutions.
Transmit - Transmit is an FTP client for Mac OS X and Mac OS Classic (which is unsupported).
TreeSize - TreeSize tells you where precious disk space has gone to.
ImageOptim - Faster web pages and apps.