As mentioned by RiOtEr
The Ctrl-Alt-Del trick, If I remember correctly worked with either 3.1 or Win95 pre-OSR2 (Don't quote me though) But that was fixed with Win95 OSR2.

As mentioned by freeOn
The reboot "trick" seems to be the easiest of all methods!

As mentioned by ammo
There are a few programs available on the internet that will show the screen saver password or disable it altogether. And the Auto-Run "trick" still works on 98...assuming they have "autorun" enabled.

My addition to this post:
I remember a time when I got curious about the screen saver and wanted to write my own program to disable the screen saver... If your curious... the Windows registry has two key values of interest:

1. ) HKEY_CURRENT_USER\Control Panel\Desktop\ScreenSaveUsePassword

And...

2. ) HKEY_CURRENT_USER\Control Panel\Desktop\ScreenSave_Data

The first determines if a password is used...It can be set to either
1 = Yes, Use a password
0 = No, Don't use a password

The second is where the "encrypted" password is stored.

My theory was that I would create a program that modified those registry keys and burn it on a CD.

I could then insert my CD and if Autorun was enabled, it would run my program...modify the keys and the screen saver would either not use a password (via the first key mentioned) or the password would be changed to something I specified (via the second key)... I don't remember writing the program...but your post has sparked my curiosity again (I might try it )

A few other interesting keys are: (if your curious)
ScreenSaveActive - Dictates whether the screen saver is used
ScreenSaveTimeOut - The time in MilliSecond before the screen saver is activated.

Hope this has helped to spark your curiosity