Electric Bikes Magazine is available free in bike shops or online or for a small subscription delivered to your .door. Full of news and test ride reviews.
Well worth visiting the Electric Transport Shop for this useful guide alone. If you live in or near London visit in person. atob gives good advice on what to look for plus a price guide and many reviews.
A superb site from Roni who has a degree in electrical engineering and is now doing a PhD in quantum physics! This site touches on almost everything. It is still partly under construction but definitely one to bookmark. The site’s title says it all: The Electric Bike Guide
There is a good overview and interesting information at Kudos Bikes website, written by their Senior Buyer, Dave Elderfield. It is completely impartial and offers excellent basic advice.