There are loads of online resources for the amateur soapmakers who want to know more about it. Unfortunately, you will find a lot of different opinions on many things, so I would generally recommend to read carefully and compare different information, and then make your own experiments in order to find out what's good or "true" for you.
This is a list of my own personal favourites, where I got many recipes and useful tips. I list the here in the hope that you will find them useful too. If you have or want to suggest other links, please comment underneath this post, and if I like the link I will include it to the list.
Here we go:
Miller's Homemade Soap: A super-useful container of first hand information and techniques compiled by Kathy Miller. It includes lye calculation, rebatching techniques, tips on how to make your own recipe, basic recipes and useful links. I simply love it!
Soap Naturally: Another very rich source of information, especially simple and advanced recipes and a clear explanation of the different soapmaking methods (cold and hot processes). It also includes and apparently amazing mailing list, to which unfortunately I was never able to register.
The Soap Making Forum: I love the forum format, but unfortunately between soapers it looks like the mailing list format is preferred. This is a pity because I believe a forum is much better organized and easier to browse. Anyway, this is one of the best and most active forums in the topic I have found so far. People use many very different techniques and have different views, but from browsing it you can get a lot of useful tips and interesting ideas. I love it.
Il Mio Sapone: probably the best Italian-language website on the subject, Il Mio Sapone includes all the useful basic information you need to start making your own soap. It includes basic techniques, easy recipes and a list of useful links and suppliers.
Nancy Today: this lovely American lady is fun to watch and although messy seems to have a good experience in making soaps. I love watching her videos because they're fun and I can usually learn a lot from her.
Anne L. Watson's Soapmaking Diary: another soapmaking diary from a person who loves to soap and to share her experience. You can find many interesting answers in there, and not just about soapmaking. There is also a useful collection of links and resource, so I strongly recommend you have a look there.
The North Country Soapmaking Library: a collection of recipes and hints from the posts of a soapmaking mailing list.
Anne L. Watson's Soapmaking Diary: another soapmaking diary from a person who loves to soap and to share her experience. You can find many interesting answers in there, and not just about soapmaking. There is also a useful collection of links and resource, so I strongly recommend you have a look there.
The North Country Soapmaking Library: a collection of recipes and hints from the posts of a soapmaking mailing list.
Here are some books I would recommend to start with the soapmaking addiction, to find new inspiration or to learn more about the whole chemistry of this wonderful art:
