Code golf: find all anagrams

Powershell, 104 97 91 86 83 chars

$k=@{};$input|%{$k["$([char[]]$_|%{$_+0}|sort)"]+=@($_)}
$k.Values|?{$_[1]}|%{"$_"}

Update for the new requirement (+8 chars):

To exclude the words that only differ in capitalization, we could just remove the duplicates (case-insensitvely) from the input list, i.e. $input|sort -u where -u stands for -unique. sort is case-insenstive by default:

$k=@{};$input|sort -u|%{$k["$([char[]]$_|%{$_+0}|sort)"]+=@($_)} 
$k.Values|?{$_[1]}|%{"$_"} 

Explanation of the [char[]]$_|%{$_+0}|sort -part

It's a key for the hashtable entry under which anagrams of a word are stored. My initial solution was: $_.ToLower().ToCharArray()|sort. Then I discovered I didn't need ToLower() for the key, as hashtable lookups are case-insensitive.

[char[]]$_|sort would be ideal, but sorting of the chars for the key needs to be case-insensitive (otherwise Cab and abc would be stored under different keys). Unfortunately, sort is not case-insenstive for chars (only for strings).

What we need is [string[]][char[]]$_|sort, but I found a shorter way of converting each char to string, which is to concat something else to it, in this case an integer 0, hence [char[]]$_|%{$_+0}|sort. This doesn't affect the sorting order, and the actual key ends up being something like: d0 o0 r0 w0. It's not pretty, but it does the job :)

Perl, 59 characters

chop,$_{join'',sort split//,lc}.="$_ "for<>;/ ./&&say for%_

Note that this requires Perl 5.10 (for the say function).