Embroidery by hand and machine can be used to embellish quilts a little or a lot.
This page has links to some tutorials by quilters who embroider and embroiders who may, or may not, quilt.
who has a blog
by Susan Brubaker Knapp on her blog
by Sandra Leichner
on her blog
gives details of the variety of needles available for handwork and is on the blog
Hand made or Machine Made Lace or Embroidery?
Article by Vincent on his blog