http://www.animenfo.com/ — A good resource for listings of anime, quick synopses, voice actors, etc. Don’t trust their reviews though; they’re full of people giving 1/10 for animation when they just hated the story, etc. That said, the overall rating is normally a vague indication of goodness.
http://www.anidb.net/ — Tends to have a much more complete selection of episode titles; also lists fansubs in a slightly more ordered fashion. They do not, however, seem to care for fansub ethics - they list a lot of not only licensed stuff, but stuff ripped off English DVDs.
http://www.anidb.net/client/ — Some client software to help you manage your collection — the WebAOM1) is a java applet that is useful for hashing your files, thereby identifying them, renaming them and adding them to your “MyList” at AniDB.net. Note that to use any of the client you need an account with AniDB.net, as the clients will ask for your login details.
http://www.animenewsnetwork.com/encyclopedia/ — Tends to have more complete credits listing, but little in the way of reviews. It proves to be very usefull when you want to know how many DVDs or manga books a series has which helps the librarian out quite a bit when it comes to ordering.
http://www.animesuki.com/ — A listing of pretty much everything available on fansub at the moment. They offer links to bittorrent sources, plus links to other big sites (AnimeNFO, AniDB, JASCII, ANN Encyclopaedia) for each series. Also has an up to date license list.
http://www.animeondvd.com/ — Lists almost every licensed anime for the last few years on their license list, and everything else in their DVD list. They review a whole lot of stuff, and they tend to do professional, unbiased and informative reviews. Both UK and US releases get listings.
http://www.animefu.com/ — Much less complete list of stuff, and is basically run by a small bunch of people who put up reviews for stuff they rent. There’s normally a few reviews for a given title, and the reviews are normally long, informative, and occasionally amusing. US releases only.
http://www.animejin.org.uk/ — Complete listings of all UK releases and gives news of all new licenses. Has a nice FAQ on buying stuff from the UK, with a good list of all the people who are busy listing stuff. Also good for http://www.animejin.org.uk/00ukrel.htm — a list of all announced releases in this country that they know of, plus normally a few months of recent releases.
http://www.mvm-films.com/ — These folks licence anime all over the board and they do it frequently too.
http://www.advfilms.co.uk/ — Licensees for about half or more of all the stuff that’s being released in the UK - and are often quite open to suggestions for new stuff to get off the US ADV.