I'd suggest that before giving it away for free check the options of 
books on demand which is really a good option. You can have an ISBN 
for the book and have good chances to appear on Amazon and the like. 
Books on demand aren't too expensive, you can start with ca. 300 
EUROs. There are quite some examples of succesful books which have 
been published this way.

Have a look at http://www.cafepress.com/cp/info/sell/books.aspx for a 
print-on-demand service. Basically, you upload a pdf with the book 
contents, choose the type of binding you want and can make a page on 
the site to advertise the book. Cafepress gets a fixed amount per book 
actually sold, and you get the margin you want to put on top of 
Cafepress's share. If I understand this correctly, there are no costs 
to you, if noone orders your book. The buyer pays your price 
(Cafepress's share and your margin) + postage, the latter dependent on 
physical location in the world. Buyer is also responsible for meeting 
tax requirements if outside U.S. Looks like a very clean and 
uncomplicated service to me, though I haven't tried it yet.

Lothar
----
Unfortunately, items sold via cafepress tend to be quite expensive, 
due to cafepress' charges. You may find it better to contact a 
printer, have them print your books in limited runs, and mail them 
yourself.

A friend of mine, Severo Ornstein, published his book with Authorhouse 
(renamed from 1stBooks). It looks like an interesting alternative. 
Severo's book is available as a download, or alternatively, on paper. 
See http://www.authorhouse.com/BookStore/SearchCatalog. aspx The book 
is also available from Amazon at a much higher price.

--Trygve