Selecting your gear
You've probably read about a switch being "managed" or "unmanaged" but wasn't really sure what that means. Basically a managed switch has an operating system running inside it that provides the ability to change various functions of each port and keeps track of traffic statistics.
Port management functions include things like being able to view port status, disable ports, mirror one port to another (handy for connecting a packet analyzer) and more. Statistics include packet, Byte, and error counts and other useful information. If you run into problems, you can quickly check these statistics and locate problems on your network without having to rip everything apart and try one thing at a time!
While it's nice to have managed switches at every position on the network, it's pretty uncommon to actually need them for your floor switches. The reason for this is that problems at the floor level typically cause problems only for one or two people at a time. Problems at the core switch, however can affect entire tables of users.
Of course cost is also a major factor - managed switches cost 2-3 times more than comparable unmanaged switches. So I recommend you purchase unmanaged switches for your table / floor switches and managed switches for core and server row switches. I also suggest having at least one spare managed switch for testing purposes or as a backup in case you have another switch go out on you at the event.
Please accept my apology if I sound like a sales guy for HP, but I have nothing bad at all to say about them. Their latest gear has an excellent and user-friendly web interface, a very powerful command line interface and all of the features you could ever want for a LAN Party - much less most enterprise businesses. Top all of that off with a lifetime warranty and you've got what I think is the best equipment available.
For the core switch of LANrental's (my company) network, we use an HP Procurve 2824 24-port 10/100/1000 (GigE) switch (Figure 3) with a very powerful backplane that is non-blocking at 48 Gbps of switching capacity.
Figure 3: HP Procurve 2824
To handle our server row area, we use the HP Procurve 2626 24-port 10/100 switch (Figure 4) with dual 10/100/1000 (GigE) uplink ports. The Procurve 2626 is also non-blocking with a 8.8 Gbps backplane. We have configured the gigabit ports in a redundant configuration (using both uplinks) and RSTP.
Figure 4: HP Procurve 2626
For table switches, pretty much any brand of unmanaged 24-port 10/100 Ethernet Switch with at least one gigabit Ethernet uplink will work fine. Just make sure to check the specifications to ensure that its bandwidth supports all the ports and uplink(s). The model switch that LANrental uses is the Dell Powerconnect 2124 - it works well for us. Note that the 2124 is no longer available, but the 2324 that replaces it should work just as well, and has two gigabit uplink ports.
Figure 5: Dell Powerconnect 2124