To open those old archives you need to get StuffIt Expander [1]. Once you have that installed, you'll be able to extract any .sit archives (unless they're corrupted).
Edit: If you're looking for some interesting software to run on OS 9, Macintosh Garden has Photoshop 7 [2] as well as Illustrator 7 [3]. It's extremely cool that you can get this old software for free now. Those applications are still highly capable for serious editing and design work.
Edit: If you're looking for some interesting software to run on OS 9, Macintosh Garden has Photoshop 7 [2] as well as Illustrator 7 [3]. It's extremely cool that you can get this old software for free now. Those applications are still highly capable for serious editing and design work.
[1] http://macintoshgarden.org/apps/stuffit-expander-55
[2] http://macintoshgarden.org/apps/photoshop-7x
[3] http://macintoshgarden.org/apps/adobe-illustrator-7