Ume 4-koma Megami Magazine
Ume Aoki doujin "RKGKMDK" from COMIC1☆5, under Apricot+ alias
Sayaka closeup as in Madoka Magica Online
Sayaka as a regular girl
Sayaka as a magical girl
Sayaka as a witch (Oktavia von Seckendorff)
The grief seed, which Madoka used for purifying Homura's Soul Gem in Episode 10's Timeline 3, may be Sayaka herself(obtained after Homura defeated Oktavia von Seckendorff, Sayaka's witch form). It bears some resemblance to Oktavia's Grief Seed from the PSP game and has what appears to be a musical staff on it, tieing in with Sayaka's musical symbolism.
According to the Puella Magi Production Note, Sayaka's sword is similar to Kyoko's spear in which the blade can break in linked pieces. It could be use to wrap an enemy with it.
According to the Guidebook, Sayaka's sword may be used as a dynamite projector. This looks more like the way in Kamen Rider than in Mahou Shoujo.
Sayaka's revised fortissimo hairpin in Manga Time Kirara Magica volume 1.