Okay, so you've already tried the tweaks on this site, but you still are hungry for a better Internet Speed. Fortunately, we do have butloads of tweaks. The one that will work best for you to increase your Internet Speed is no doubt this one. Okay, shall we start?

                                                                   

Like always, these are the pre-requisites:

FireFox
This obviously needs no introduction, 
but if you're using some other browser,
then I really recommend you to switch to 
FireFox immediately.

FireTune
Here we present you, a mind-blowing tweak 
for FireFox, which gives your Internet a 
new high, thus providing optimum 
browsing experience.

Got 'em. What now? Lets get going:

I'm assuming that you're already installed and using FireFox.

a) Install it. After installation, Click on "Create backup configuration" first.

Please click the above image to enlarge* (Popup blocker must be disabled)

b) Next, choose the settings according to your needs and computer configuration. Be sure to check out the other two tabs viz. "Other Optimizations" & "Other useful settings" too.

c) Click Tune It! (FireFox should be closed first).

I recommend using FireTune once every one week. Reason being, from my personal experience – My Internet Browsing Speed increases after using FireTune once. But it changes substantially, and reverts back to the old speed after some days. Just make sure you have a backup of your previous configuration (Prevention is better than cure, duh!).