Depends on the particular format, but you could try "Stuffit Expander" from Aladdin for "sit" or "hqx" formats. Although you can uncompress them does not mean you will necessarily be able to actually "use" them.
The information on Computing.Net is the opinions of its users. Such
opinions may not be accurate and they are to be used at your own risk.
Computing.Net cannot verify the validity of the statements made on this
site. Computing.Net and Purch hereby disclaim all responsibility
and liability for the content of Computing.Net and its accuracy.