This is a good question that comes up every once in a while. As you can see from the answers in the links below,there are alot of factors that come into play.The consensus from everything I have read would be 20-30 users per AP depending on actual applications etc.Have a read for some great answers provided in this forum by some "hands on" experts:
Here is a cisco doc that relates to this question;
Q. How many clients can associate to the AP?
A. The AP has the physical capacity to handle 2048 MAC addresses. However, because the AP is a shared medium and acts as a wireless hub, the performance of each user decreases as the number of users increases on an individual AP. Ideally, not more than 24 clients should associate with the AP because the throughput of the AP is reduced with each client that associates to the AP.
MAC address filters allow or disallow the forwarding of unicast and multicast packets either sent from or addressed to specific MAC addresses. You can create a filter that passes traffic to all MAC addresses except those you specify, or you can create a filter that blocks traffic to all MAC addresses except those you specify. You can apply the filters you create to either or both the Ethernet and radio ports and to either or both incoming and outgoing packets.
Note: Using the CLI, you can configure up to 2,048 MAC addresses for filtering. Using the web-browser interface, however, you can configure only up to 43 MAC addresses for filtering.
Transferring Crash file from standby: Login to the Active WLC in HA.
From CLI: (Cisco Controller) >transfer upload datatype crash (Cisco
Controller) >transfer upload filename (Cisco
Controller) >transfer upload mode tftp (Cisco Controller) >transfer
This is the start of a display filter cross reference between Wireshark
and OmniPeek. The 1st installment is a table of advanced filters. More
filters will be added as time allows. It is a living doc, so check back
for changes every so often Please feel f...
I have created a Powershell script to automatically add a Wireless Guest
User on Cisco WLCs. (tested on 2500 Series) The script should be
completely self explanatory. Prerequisites: Powershell SNMP Module
(Install-Module -Name SNMP) SNMP Write Access to y...