After a short discussion on the ID forum, drf has suggested a thread here to drop the names of the smaller and less well known foundries that people may have come across in their travels through cyberspace (and the real world).
It is fitting to kick off with $10 Fonts, as it was them that the discussion was about.
http://www.tendollarfonts.com/products
Work from here has been surfacing on the ID forum quite a lot, and they seem to be adding, interesting fonts on a fairly regular basis.

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FontFabric : http://fontfabric.com/category/free
K-Type : http://www.k-type.com/?cat=6
Legacy of Defeat (Hydro74) : http://legacyofdefeat.com
LetterHead Fonts : http://www.letterheadfonts.com
Lost Type : http://losttype.com/browse
Maniackers : http://www2.wind.ne.jp/maniackers/designfont.html
Signfonts : http://artandsignstudio.com/fontmenu.html
Ten Dollar Fonts : http://www.tendollarfonts.com/products
The League of Moveable Type : http://www.theleagueofmoveabletype.com
Type Depot : http://www.typedepot.com

Awesome You talked about Lost Type, so here it is : http://losttype.com/browse/

They get more and more known ! Their fonts are also identified quite often around here.

May I add Legacy of Defeat, they have some free fonts, and some of the rest isn't very expensive either, especially considering the real originality of their work.

http://legacyofdefeat.com/

If we are having Legacy, we'd best include Hydro direct
https://www.merchline.com/hydro74/category.3998.c.php
Since he's also very reasonably priced, and it's his freebies on Legacy

I bookmarked this link a few months ago : http://www.typedepot.com/

Some for free, some for sale on Myfonts.

Good job

http://www.letterheadfonts.com/

A post from SashiX just reminded me of this one : http://www.theleagueofmoveabletype.com/

Have to have a mention:
http://fontfabric.com/category/free/

Signfonts
http://artandsignstudio.com/fontmenu.html

Maniackers
http://www2.wind.ne.jp/maniackers/designfont.html

(pilaster, i edited your first post to make the list bigger)

Good stuff. Consolidating the list will make it more manageable.

K-Type
http://www.k-type.com/?cat=6

K-Type added to the list