Do sub domains rank as well as normal domains
 

i never see any listed

that's your answer

yes they rank even better than domains

What about blogger, tumblr and sites of that nature, where EVERY user has a sub-domain?

Type "craigslist" into Google. Chances are you get results for your local city or a city that you've been researching which are all on craigslist subdomains.

what about en.wikipedia.com

subdomains rank well and they give the main index page/domain a big boost in authority.

build a few, get them backlined @ www.hardlinks.org and watch the results

I have a small *test* blog network which uses 1 main domain and 10 subdomains....the subdomains get some pretty decent SE traffic.

Personally, subdomains rank ok. I prefer to let make my Wordpress multisites in subfolders.

When I search Google, I rarely will click on blah.blahblah.com unless I recognize the site because it just looks shifty. I personally prefer blahblah.com/blahstuff as it presents a more coherent website identity to me.

subdomains can rank just fine, www is a sub domain ;-)

Do you guys like sub domains linktrade from your top level domains with sub domains?

:thumbsup

cant compare that to a general subdomain, like for example: porn.crappydomain.com.
It's a language subdomain, completely different.
If you try to rank a subdomain like my example, dont bother. I even believe subfolders (like crappydomain.com/porn/ ) are better.

what ^^ said.

www is also a subdomain.

Of course they can; you can have your site rank for multiple terms by going for different ones with each sub-domain. . . . . and www is a subdomain

So i could have
domain.com
new.domain.com
domain.com/new