Set up your router for your PS3
First, I recommend going to www.speedtest.net
on your PC connected to the same router your PS3 is connected to. Use this site to test your connection speeds. This sets up a baseline for comparisons elsewhere. You can try it a few times to get a good average.
Once you've got that, do the same thing on your PS3. Use the web browser to open the same site and choose the same test locations, and do it a few times. In my testing, my home PC was about always faster downloading than the PS3, who knows why.
When I first started, I was getting 26x faster on my PC. So, I jumped in to my router settings. If you don't know how to do this, check your vendor's site, they will often have specific instructions on how to access your router's management software.
If your router has any QoS settings, turn them OFF. QoS usually does NOT work at all, and believe it or not, your router has a CPU in it and it's not very fast, and everything your router does to your packets affects it's speed. This option can usually be found around the wireless settings.
QoS is an advanced feature that can be used to prioritize some internet applications and on-line gaming, and to minimize the impact when the bandwidth is busy. When I turned this off, it quadrupled my speed scores. This option can usually be found with the wireless settings.
If your router has Wi-Fi Multi-media (WMM) Settings, disable those also. Again, this is similar to QoS in that it doesn't work. Turn it off.
When I disabled this, my speed scores doubled again.
If your router has any SPI (Stateful Packet Inspection) Firewall firewall features, I recommend disabling those, since they will slow you down. This can, in theory, reduce the protection of your router, effectively allowing you to get DoS attacked, but how often does that happen? And besides, your router shouldn't be responding to internet ping's anyway.
I've never allowed this feature to be on, so I've got no comparisons for speed here.
If you have trouble staying connected to PSN, or you find that you can't join games, your router might be messing up NAT traversal (or might not support it). NAT traversal is a special way to allow your PC to connect and play with people over the internet without having to configure your router to forward packets on a specific port range to your PC. It basically says "Dear Router, this packet needs to go this PC!" If this is happening to you, you might have to "Open" or "Disable" NAT filtering, which prevents packets from telling the router where they should go.
You can also put your PS3 in the DMZ (De-Militarized Zone) of your router, this prevents ANY interference by your router.
You could also open ports 28900 (TCP) and 27900 (UDP) for outgoing, and open up 6500, 6501 for unsolicited UDP traffic. These are the most common ports that GameSpy uses for matching, and if NAT traversal isn't working for you, you might need to forward these ports to your PS3.