We have had all sorts used to advertise peoples stores if you read through, this part of the forum a lot of them have groups, that you can join.
You can add links on most of the P2P things and list your products or info.
# facebook
You can find the group on here
# Friend feed
Not used it yet
# My Space
You can find the group on here
# Twitter
Everything you post is posted to your friends but the owner prevents it from being rated by google, so the links will not help a website rating.
# Squidoo
A bit like blogger.
# Delicious
Still not used it
# Digg
Still not used it so not sure what it does
# Second life
Interesting idea, and if your computer is up to it, then you may find it useful. You can find more about it on here, I think they will also do it for you if you ask them and add a link to your store at Manderley Manor, but I think there is a small charge.
# Blogger
You know about, Check out the gadgets that you can add to interest your customers Either the ones available or the ones from igoogle
# Flickr
You have seen a fine example of that above
# stumbleupon
# technorati
Social Bookmarking the same as Digg and Delicious
There are also others that I have never even looked at yet such as MIxx, Yahoo Buzz, Redditt, Propeller. So no idea what they do, Just know I can post pages direct from firefox.
And some are also using things like Wikapedia, YouTube. Youtube is being used a lot, if you have a bit of skill with a film editor of some sort.
With most of these you can add things direct from the page your on, such as your products, either from tools on the sites in question like Squidoo or by using tools on firefox.
Also a lot of them have ebid groups set up, which you will be able to find by following the threads on here. You may find some good info if you read through those threads
You can find the links to a lot of them and some other stuff you can use like search engines, and stuff on one of my blogs here.
http://asitisso.blogspot.com/
If I find any others I'll add them or people can tell you more about those listed