Book 4: Goblet of Fire unfinished
Harry Potter accidentally mistakes Winky for our favorite little house-elf, Dobby. He sees a creature whose "long, batlike ears were oddly familiar...." (97) It was instead a female named Winky, with with "a nose the exact shape and size of a large tomato ... [and] a voice higher even than Dobby's had been, a teeny, quivering squeak of a voice" (97)

Book 5: Order of the Pheonix
Hardly mentioned except in a negative tone, she's still important. It turns out some of the clothes Hermione has been making were given to her. "Winky is still drinking lots, sir ... she still does not care for clothes, Harry Potter." (pg. 385). When discussing the Room of Recquirement, "Dobby has used it, sir, when Winky has been very drunk. He has hiddden her in the Room of Requirement and has found antidotes to butterbeer there, and a nice elf-sized bed to settle her in while she sleeps it off, sir." (pg. 387)

Kreacher
How does Kreacher help the story along? Why is he and the other hous-elves cruicial to the story? (WARNING: SPOILERS)

Book 5: Order of the Pheonix unfinished
A crucial part to the story, however, not looked very highly upon, even though I enjoyed his character - he's like the opposite of Dobby in some ways, however very much the same in others.