A number of people have been building up databases of teachers over the years, containing varying amounts of biographical detail and information about their teaching. Some also attempt to assess their ability or authenticity and can be quite scathing about those of whom they do not approve!
There are many modern Sages who periodically engage in tours to various countries where they give short satsangs, weekend 'intensives' or residential courses. Most of the students who attend these sessions have been 'seeking' for many years and are very knowledgeable in the theory. Consequently, many of the questions that are posed are from the vantage point of this extensive knowledge and may go 'over the heads' of novices. It is therefore advisable that one studies and practises sufficiently to know what one is talking about before searching out a teacher. (Ideally, one should also read the book mentioned elsewhere so as to be aware of the many pitfalls.)
Before the advent of the Internet, of course, it would almost certainly have been the case that only the very serious seeker could have found a teacher in the first place. Nowadays, though, anyone who can use the search engines can find the nearest venues with very little effort. This means that someone with only a passing interest in the subject can turn up and disrupt a group by asking silly questions. If you have reached the stage of needing answers from someone who actually has them, the task of deciding who to see can be daunting. Here, the Internet definitely comes into its own. It is possible to find information about them and download samples of their dialogues. It is then relatively easy to discover someone whose language seems to strike a chord.
Guru's Feet - a meeting place for spiritual people This is the largest site I have come across for guru listings. When I looked, there were over 800 teachers listed, from all sorts of traditions. The table lists name (including a small picture for most), type, tradition(s), country, whether still living, and time entry last updated. There is then a page for each, giving factual information such as descendent and related gurus, date and placeof birth etc with a large image and a detailed biography and information about their teaching. The material is gathered from sources such as Wikipedia but can be updated by visitors. An excellent resource!
There are also sections for blogs, forums, events and 'goodies'. Also networking and online temple, but you need to subsribe for these. It should be noted that the topical material tends to be 'new-agey' or 'neo-', as you would expect. And, since gurus are entered by users, the keywords used for 'type' and 'tradition' tend to vary, with teachers being classified as 'satguru', 'jnani', 'avatar', 'master', 'spiritual teacher', 'sage', as well as simple 'guru'.
List of teachers, gurus and realizers A comprehensive list, from which most other lists on the web derive. It provides a link to each teacher listed together with their location and a quotation from their teaching.
Sarlo's Guru Rating Service was excellent. There were many entries, though some of the descriptions appeared to be somewhat disrespectful! I have just discovered (Nov. 2011) that the site has changed its address. It looks as though it is in the process of development and practically all of the material that used to be there has not (yet) reappeared.
In The Light - This New Zealand site has brief biographies, pictures etc. of 'world teachers', both current and throughout history. The list is now very comprehensive indeed.
Strictly Spiritual is Shawn Nevins' site, containing some valuable guidelines on how to choose a teacher as well as some personal ratings of a number of teachers, past and present. There are also reviews of films and books with a non-dual slant and a message board.
Clearly views from one who is not him/herself enlightened are bound to be subjective and liable to error. Since a Sage does not discard the nature of the body-mind entity upon Realisation, a guru may exhibit all manners of idiosyncrasies. Rick Ross' site contains news articles about cults and dubious teachers, though these too must be treated with care.
There is a book, called 'Coming Home, An Invitation to Rediscover our True Nature' by Jan Kersschot, that includes interviews with a number of teachers. Extracts may be read at the site.
See also the book by Paula Marvelly - The Teachers of One.
Another book, called 'The Awakening West' by Lynn Marie Lumiere has interviews with Adyashanti, Peter Fenner, Gangaji, Douglas Harding, Catherine Ingram, Kenny Johnson, Francis Lucille, Satyam Nadeen, Mira Pagal, Robert Rabbin, Byron Katie, Rolle, Isaac Shapiro, Lama Surya Das, Christopher Titmus and Eckhart Tolle. This is a newly published version of the book.