Google, eBay and Friends Reunited are among key influential websites which have had the biggest impact on UK web users, say analysts Nielsen Netratings.
Online auction site eBay has a reciprocal element
Early commerce and price comparison sites like Amazon, Kelkoo and Easyjet, have paved the way for online shopping.
While community-based ones like file-sharing network Napster, web diary site Blogger, and AOL Instant Messenger are named pioneers in the top 10 list.
Nielsen Netratings have been monitoring online trends for the last five years.
"We have picked these sites because we think they are the ones that have changed the way people see and conceptualise the web," Tom Ewing, Nielsen Netratings analyst, explained to BBC News Online.
"What the list suggests is that the vision of the net is as an interactive medium rather than a broadcast one."
The ability to make friends and enlarge social networks has proved to be a popular use of the net over recent years, he added.
"It shows the reciprocal element of the net too. You as a user can put more in to get more out.
"The rise of sites like Friends Reunited and Blogger also shows a rising confidence of people wanting to put themselves on the net and letting other people into their lives."
TOP 10 MOST INFLUENTIAL SITES
Microsoft Outlook e-mail
AOL Instant Messenger
Source: Nielsen Netratings 2003
Web users are getting so confident, they feel much more at ease getting involved in online selling too, through auction sites like eBay.
EBay has now become the biggest e-commerce site in Europe, suggesting many have overcome their fear of online shopping.
Leading website Google, essentially a searchable web database, has become so ingrained in the average web user's online psyche it has even mutated into a verb itself.
To "google" someone means to look up information about them on the net.
Mr Ewing has predicted the concepts behind these websites will prevail into the next year.
But because of the fear of threats to child safety online, computer viruses and hacking, web users will want to create more personal, private spaces online.
"Most sites that have been successful this year have been ones that are public spaces - like market squares," said Mr Ewing.
"The next thing will be how they can be used to exploit the private net.
Napster helped people get familiar with digital formats
"People will want to create private spaces, in instant messaging programs for example, so that they can share areas."
He is also predicting that broadband net allowing more net radio and TV, as well as the growth of file-swapping sites, will continue to change how surfers view and use the net.
File-sharing sites like Napster have helped to familiarise people with emerging digital formats, like MP3s.
This in turn has helped fuel the explosive popularity of sites like Apple iTunes and digital jukebox gadgets, like the iPod.