Simulating Slow Internet Connection [closed]
Starting with Chrome 38 you can do this without any plugins. Just click inspect element (or F12 hotkey), then click on "toggle device mod"
and you will see something like this:
Among many other features it allows you to simulate specific internet connection (3G, GPRS)
P.S. for people who try to limit the upload speed. Sadly at the current time it is not possible.
P.S.2 now you do not need to toggle anything. Throttling panel is available right from the network panel. 
Note that while clicking on the No throttling you can create your custom throttling options.
If you're running windows, fiddler is a great tool. It has a setting to simulate modem speed, and for someone who wants more control has a plugin to add latency to each request.
I prefer using a tool like this to putting latency code in my application as it is a much more realistic simulation, as well as not making me design or code the actual bits. The best code is code I don't have to write.
ADDED: This article at Pavel Donchev's blog on Software Technologies shows how to create custom simulated speeds: Limiting your Internet connection speed with Fiddler.
Google recommends:
- Network Link Conditioner on OSX
- Clumsy on Windows
- Dummynet on Linux
On Linux machines u can use wondershaper
apt-get install wondershaper
$ sudo wondershaper {interface} {down} {up}
the {down} and {up} are bandwidth in kpbs
So for example if you want to limit the bandwidth of interface eth1 to 256kbps uplink and 128kbps downlink,
$ sudo wondershaper eth1 256 128
To clear the limit,
$ sudo wondershaper clear eth1
I was using http://www.netlimiter.com/ and it works very well. Not only limit speed for single processes but also shows actual transfer rates.