MarketingSherpa hosted a teleseminar on Dec 3 on the some of their latest email stats. There is a recording and PowerPoint slides that features 11 useful charts on budgeting, open rates, filters, click trends, conversion rates, and gathering opt-ins.
PDF of PowerPointSlides: http://www.marketingsherpa.com/tele/SherpaEM.pdf
Audio (approx. 60 minutes): http://www.marketingsherpa.com/tele/mrktsherpa120304.wma
eINFO - a collection of articles and studies about email marketing