I am a newbie in the world of web3d and am interested in learning about it starting at the basics of COLLADA. Where is the best place to start?
Here is a good place
But to answer your question, COLLADA can be approached from different angles.
If you are familiar with DCC package, you can download the corresponding plug-in. You create some content, and look at it in the COLLADA form. I personally recommend using XML spy (free for personal usage) for this.
Alternatively you can start with the COLLADA specification on the Khronos web site. If you are familiar with XML technology, you can look at the Schema directly. It is good to look at the schema anyway. Using XMLSpy you can see it in a graph rather than looking at the text form.
If you are a programmer, you want to check out the COLLADA DOM, on sourceforge, and in particular play with the conditioners examples, that are small programs that will let you load/transform/save COLLADA documents.
Also, A.K. Peters announced during GDC that they will be publishing a book about COLLADA at SigGraph. so this will be a good place to start this summer.