Mozilla Firefox itself is the best internet browser available and it's free! User created addons and themes enhance the Firefox experience. This article will cover my favourite five.
Stumbleupon is a toolbar which is added to your browser which links to a community of millions who have also got the addon. When you first download the addon it will take you through a registration process where you outline you interests in quite a lot of detail. When you then click on the "Stumble!" button in your browser it takes you to a random website bookmarked by another user which matches to your interests. This is a fantastic service which has found me all my favourite sites and services.
There are many addons with a similar purpose to sxipper but I have found it to be the best. Sxipper is a secure addon where you record all your information, usernames and passwords, addresses - both physical and email and when you are confronted with a form, say for registering to a new website it can automatically fill in all your information for you. It can also be used to automatically log into services you ahev already registered for.
Although many may think this is a trivial addon I have found it extremely useful and very accurate. The weather forecast service is provided by accuweather a global weather forecaster. You simply register your location and change whatever options you want to change your view and you have an accurate weather forecast for the next few days and even a picture from a satellite of your area (not very useful but it certainly looks good)
For those who need the more security than even firefox can provide, Noscript is the addon for you. It prevents unknown websites using potentially malicious software such as java, javascript and flash on websites you view. Their motto is "there is a browser safer than firefox. It's Firefox with Noscript!"
Interclue allows you to see through a link and see whats on the next page without actually going there. It provides a summary of the page in a small box and allows you to quickly see what is on the next page.
Firefox has many useful addons and the above five certainly excel in their categories and I fully recommend them to you just as I recommend you get Firefox.
Cooliris preview is better than interclue....I suggest cooliris preview than interclue.