As far as actual browsing speeds go I know of no way to improve that other than some tweaks to windows that I am sure others here can give you. As far as increasing dl speeds it is possible by using a download manager such as down load accelerator by speedbit. What this thing does is open multiple instances of downloading the same file in pieces. It then reasembles them to the file you requested. I found this to be very effective when I was using satellite for internet because they afforded you more bandwidth for dl multiple files. However I have not found it to be helpful on my dsl line unless I am dealing with a slow website. I am allowed 1.5mbps regardless of the number of files I am dl'n
Download managers and stuff will just better utilize the bandwidth avaliable. You can't actually exceed your rated speed. A 1.5megabit connection will never download over 192kb/s, it just isn't possible.
There really isn't anything you can do at your end to physically increase your connection speed.
What are your current download speeds (kilobytes/s) and what does your ISP say your connection speed is (kilobits or megabits).