Along with the Derveni and Timotheos papyri, the document known as the "Curse of Artemisia" (P.Vindob. G 1) represents one of the oldest surviving papyri in Greek. It is dated to the 4th cent. BCE and is written in an "epigraphic" style typical of the period. It was found at Memphis and is now housed in the Papyrus Collection of the Austrian National Library, Vienna. The letters are a bit clumsy and imitate those of stone inscriptions (theta with middle dot, omega with flat "arcs," sigma as a wedge, an intermediate form between epigraphic and lunate forms). Kenyon states that the papyrus "is not the work of a professional scribe, but the writing of an uneducated woman who uses uncial letters because she can form no others [...] such letters were commonly before her eyes in public places, while she had probably seldom seen a book" (Palaeography of Greek Papyri, Oxford, 1899, 57). This non-literary papyrus demonstrates that there was very little difference between literary and non-literary scripts in the 4th century BCE. A translation of this interesting papyrus may be found here.
The World Digital Library has a page devoted to the Curse of Artemisia, which includes a nice introduction and description. More important, there are images there of the best quality. Click on the image and it will open up a screen which allows one to zoom in; the resolution is exceptional. The image can also be downloaded from the site as a PDF or PNG.
Update: See the nice post about the Curse of Artemisia at Judith Weingarten's blog, Zenobia.