Recently I had been having some internet speed problems. There are several basic checks you can do yourself such as double checking your wired connections are all plugged in properly, making sure you are logged onto the correct wi-fi network :) and so on. You can even check to make sure your modem or router is not overheating (I once had one that was smoking).
So here are some tests you can run if you think you might have a problem, and what the heck, check it even if there isnt a problem so you know where you stand.
Pingtest checks your line quality by examining packet loss, ping rate and jitter rate. Low jitter means you have a stable connection.
Give yours a test here: http://www.pingtest.net/
I also like to use M-Labs Network Diagnostic Test (java required). Besides the basic up/down speeds, it also has sophisticated diagnosis of any problems limiting your speed.
Check it out here: http://www.measurementlab.net/tools/ndt
M-Labs also has NPAD test (Network Path & Application Diagnostics; java required) which is designed to diagnose network performance problems in your end-system (the machine your browser is running on) or the network between it and your nearest NPAD server (basically the last mile or so of your broadband). For each diagnosed problem, the server prescribes corrective actions with instructions suitable for non-experts.
Finally, you can also install NEUBOT (Ubuntu Linux, Windows, Mac). Neubot is a research project on network neutrality. Transmission tests probe the Internet using various application level protocols. The results dataset contains samples from various provides and is published on the web, allowing anyone to analyze the data for research purposes.
With this software you can also check to see if your internet service provider is throttling your internet speed for any reason.
Learn more & how to install here:
Ubuntu users can easily install with DEB file...
At home I determined my wi-fi card was the problem and replaced it. At work, I found my ISP was throttling internet speeds when using Deluge (a bittorrent-like app). Knowledge is power!