Another couple of older completed series that I especially enjoyed and wanted to share:
Shoujo Fujuubun (Imperfect Girl) - written by Nisio Isin (which IMO should be sufficient recommendation all by itself), ~~it's quite short at only six chapters~~ and is frankly astonishing. It's more a coming-of-age drama than anything else, but really defies description. Just read the first chapter and I can pretty much guarantee you'll be hooked.
ETA - I screwed that up entirely.
I thought six chapters seemed short, but I haven't actually read it in a couple of years, and I was going by what Mangadex has.
It's actually 27 chapters (I know - that's a pretty significant difference). Apparently Mangadex just doesn't have the rest (and the original version of this post linked to them, but obviously that was a waste of time).
But everything else I said about it still holds (I'm sure of that because I discovered my screw up when I set out to reread it).
The full run is available at least on MangaSee, under the English title, but I don't know if I can, or should even if I can, directly link it here. I still strongly recommend it.
My apologies to anyone who was misled or confused by my utter failure.
A Methed to Make the Gentle World (Yasashii Sekai no Tsukurikata) - a very well done coming-of-age romance comedy/drama with an emphasis on character development. Fairly short at 31 chapters, and with a very satisfying ending. And for what it's worth (it's not really significant but does amuse me), while most current manga sites changed the spelling and phrasing of the English title or even substituted the Japanese title (as Mangadex has done), that English title, with that exact phrasing and spelling, is actually the title it was originally published under in Japan.