Some resources on EM:

• The original Expectation Maximization paper.
• A “gentle” tutorial on EM. Its actually not very gentle and talks primarily about Gaussian mixtures and HMMs.
• As always, don't forget the wikipedia page on EM.
• Wapedia has a great page on the topic.

On K-means:

• Stuart Lloyd's original paper on the Lloyd quantizer. The paper originally appeared in BSTJ (Bell Systems technical journal) in 1952.
• MacQueen's original K-means paper.
• The wikipedia page on K-means
• And wapedia has a better one.
• The original Linde Buzo Gray paper on vector quantization.