I must admit, the tools for Reader's Advisory are something that I've had a bit of trouble getting a handle on for this class. That is to say, I sort of expected to find a few good websites and that would be biggest part of it. The fact of it though, is that there really are not just a few really good places to go, for the most part. What I've come to find throughout the book presentations and the Reader's Advisory lab is that there are many sources that one may have to sort through, and not just a few authoritative ones.
Books such as Saricks's The Reader's Advisory Guide to Genre Fiction can be a great tool for librarians and individual readers alike. By reading through that book, I have found several books that I would like to read. Actually, a few that I read for this class came from suggestions in that book. Librarians could of course find this book useful, but the downside is that the suggestions contained within are limited by space and by publication date of this book.
The online sources offer much more, of course. They can add titles immediately. But still, it can be difficult at times to find a good tool, or even a good list made by another librarian, to match what someone is looking for. There are a multitude of options, and it can be difficult to sort through them all. The genre specific ones seem to be the best really, which makes sense, since they have more focus (e.g. Fantastic Fiction, and Stop You're Killing Me). I especially found Fantastic Fiction to be good. Literature Map is okay, but it doesn't always hit the mark. Also, they only give authors, not titles.
One problem that I've run into on more than one occasion is that some of these sources, such as Novelist, require a subscription. This wouldn't be so much of a problem for libraries (although, if it costs money, that could be an issue), but it doesn't really help individual users much. I came across a few sites that were kind of difficult to navigate.
Often, if I was looking for a lesser known author, or non-fiction, I found myself having to go to google.com and searching the subject+read alikes. Sometimes I would find some good sources there, like a page a librarian had created for something specific, bit it involved a lot of sifting through the junk to get the good stuff. Sometimes, I had to look through Amazon.com recommendations. There actually is some good stuff there, but it is based on sales. Although, if one takes a few seconds to look through their reviews, sometimes recommendations can be found there as well.
I am, of course, new at using these tools, finding the tools, and using them effectively. I suppose if I were to do this on a regular basis, I would find some reliable sources and cut down on the time spent "sifting throught the junk."