Hello. I'm also interested on this. On regular basis I look for each new series I start reading here on spanish-language sites and sometimes I find that there are more chapters on those sites. So, if there are no new english chapters released in a while I tend to read the spanish translations. I kinda hated those translations before because they were horrible and senseless, but lately I'm happy to say that there are very good translation works released by spanish-language groups. There are several works without entries on mangaupdates that have the first chapters released by these groups before they appear here or elsewhere in english.
Perhaps you are looking to scanlate these works to english? Or you are like me and just want to read them?
Anyway. Here are some that I think qualify to an answer to you, but with variable quality (some are almost unreadable):
[ul]
Tenshi to Akuto!! <- Very good
Dance in the Vampire Bund A.S.O. <- Good TL, so-so story
Machigatta ko wo Mahou Shoujo ni Shite Shimatta <- Very good TL
Cardcaptor Sakura – Clear Card Arc <- Not so good TL on the latest chapters
Dungeon ni Deai wo Motomeru no oratoria
Dungeon ni Deai wo Motome Ryuu
Dungeon ni Deai o Motomeru no wa Machigatte Iru Darou ka
Hajimete no Gal
Arifureta Shokugyou de Sekai Saikyou
Real no heroine wa irimasen!
Isekai Maou to Shoukan Shoujo no Dorei Majutsu
Freezing
Tensei Shichattayo (Iya, Gomen)
oku sama ga seito kaichou
Ane Log Moyako Nee san no Tomaranai Monologue
Minamoto kun Monogatari
Oresama Teacher
naze boku no sekai wo daremo oboeteinai no ka
Shouwa Otome Otogibanashi
Parallel paradise
fire rabbit
Harapeko no Marie
soukyuu no ariadne
Isekai Maou to Shoukan Shoujo no Dorei Majutsu[/ul]
Some of these are on par with the english release now, but at some time they were ahead on spanish. I'm sorry if there are english releases ahead of these, but It's possible that they exist out there on some form and I didn't know about them.
