Church of Sinvention

Another site offering nice and robust looking leather (and vegan) collars.  These particularly took my eye because of the subtle addition of the hardware, instead of being big plates it looks smoothly riveted on and integrated almost:

Church of Sinvention

Corporal Dale

If you fancy some nice robust looking custom leather collars you could do worse than looking here, same site also offers paddles, slappers, restraints, cuffs, etc.etc.etc. in fact almost anything made out of leather:

Corporal Dale Leather Crafter

Fantasies in Leather

If you're looking for some interesting contoured collars (and others, including some nice flat silver ones) then you may wish to check out:

Fantasies in Leather

Harlequin Collar

Okay this is another one I can't link to due to flash inaccessible peril, but its quite awesome.  Fetish N Leather make a collar called the "Harlequin Collar", from the main site select "Store", then "Collars" then check the Harlequin Collar

Fetish n Leather

Molloss

Okay totally worth viewing for the introductory flash if nothing else, one part shakey-cam one part disturbing music video background, sadly this means its deep linking and accessibility fail as far as I can tell.  The collars themselves also appear to justify the atmosphere on the site, looking robust and beautifully industrial.

Molloss Master

Vegan Collars

Okay so some people who like collars dislike using animal products (which in my opinion means they should go for metal Mmmm metal) however if they want something nice and flexible what are they to do?  Well the people over at Vegan Erotica believe that being kinky and being vegan are not incompatible:

Vegan Erotica Collars

Dungeon Delights, Red goodness

Next up is an interesting collar in terms of colour scheme, both metal and bright metallic red.

Simple Elegance Collar 1 inch wide with 1 Ring