Okay here's my computer running every app I have installed. I should have installed Office too, but I don't use it and I don't need MS bloatware crashing Classic and ruining my fun.
One note, the system ran fine with all of this going on. Launching an app was slow, but working in a currently running app was painless and quick.
Here's a list of what I had running. I'd have launched more if I had more.
OmniWeb
Mail
GraphicConverter
Terminal
Process Viewer
TextEdit
Loadindock
ManOpen
PandoCalendar
AIM
AOL Carbon
Fire
Address Book
Clock
Chess
Image Capture
Internet Connect
Help Viewer
iTunes
Preview
QuickTime Player
Sherlock
Stickies
System Preferences
Apple System Profiler
Applet Launcher
CPU Monitor
Console
DigitalColor Meter
Directory Setup
Disk Copy
Disk Utility
Display Calibrator
Grab
Installer
Key Caps
Keychain Access
NetInfo Manager
Network Utility
Print Center
ASCII Table
Clean Text X
Cronnix
Droplet Builder
FreeSpace
Flame
MoreCalculator
Notes
OpenUp
SoundEdit 16
StuffIt Deluxe
Son of WeatherGrok
TinkerTool
WebPics
ICQ
MSN Messenger Service (Classic)
OmniDictionary
RBrowser
Graphing Calculator (Classic)
SimpleText (Classic)
Double
MacSolitaire
Spaceward Ho! (Classic)
And here's the picture.
Lots of apps running here
One note, the system ran fine with all of this going on. Launching an app was slow, but working in a currently running app was painless and quick.
Here's a list of what I had running. I'd have launched more if I had more.

OmniWeb
GraphicConverter
Terminal
Process Viewer
TextEdit
Loadindock
ManOpen
PandoCalendar
AIM
AOL Carbon
Fire
Address Book
Clock
Chess
Image Capture
Internet Connect
Help Viewer
iTunes
Preview
QuickTime Player
Sherlock
Stickies
System Preferences
Apple System Profiler
Applet Launcher
CPU Monitor
Console
DigitalColor Meter
Directory Setup
Disk Copy
Disk Utility
Display Calibrator
Grab
Installer
Key Caps
Keychain Access
NetInfo Manager
Network Utility
Print Center
ASCII Table
Clean Text X
Cronnix
Droplet Builder
FreeSpace
Flame
MoreCalculator
Notes
OpenUp
SoundEdit 16
StuffIt Deluxe
Son of WeatherGrok
TinkerTool
WebPics
ICQ
MSN Messenger Service (Classic)
OmniDictionary
RBrowser
Graphing Calculator (Classic)
SimpleText (Classic)
Double
MacSolitaire
Spaceward Ho! (Classic)
And here's the picture.

Lots of apps running here
