The scikit-learn digits dataset: 1,797 tiny 8x8 greyscale images of handwritten digits, and the workhorse of every sklearn tutorial that needs a multiclass problem which loads instantly and fits in L2 cache.
Provenance
The data is the Optical Recognition of Handwritten Digits (optdigits) set from the UCI machine learning repository, created by E. Alpaydin and C. Kaynak at Bogazici University and donated in July 1998. It originates in Kaynak’s 1995 MSc thesis on combining multiple classifiers, and the companion paper is Alpaydin and Kaynak, Cascading Classifiers, Kybernetika 34(4), 1998.