These are old versions of extensions whose newer versions dropped SeaMonkey compatibility, no longer hosted by their author, and extensions that just disappeared. They are preserved here.
Extension Room says:
Hides the toolbars when entering full screen, and contains features like, A la IE floating, customizable static bars, etc.
Download AutoHide 1.0.1
Always Remember Password
Makes websites always remember your password, even if they don't allow it.
Download Always Remember Password 0.3
Gives you more control over animated GIF images on web pages.
Download Page Animation 0.5.5
The name speaks for itself.
Download Linkfilter Toolbar 1.4.1
Clear Private Data
Equivalent to Firefox' Clear Private Data feature. Erases your cache and history with a single click.
Download Clear Private Data 1.0