Locating specific competitors?
I'm sure that you've probably conducted a number of searches to see if you could find other sites that offer celtic crafts. If Google isn't helping you, you might want to try Yahoo! and MSN, too. I would definitely look in more than one search engine. I'd also use a site like this one which shows how certain terms rank in both Google and Yahoo! for certain terms at the same time:
Try some other terms that might what your potential customers will search for.
You'll also want to try to find offline competitors, too. Those might be a little harder to locate, but you should be able to find where the biggest markets are. I'm going to suspect that some of those may still engage in catalog sales, and in news letters online. Of course, you will want to get copies of things like those catalogs and newsletters.
If you can get a copy, you might want to look through an issue or two of the Maine Antique Digest - see http://www.maineantiquedigest.com/
If you can't find a copy, send me a PM or an email, and I'll see if I can send you a copy. My local news stand carries it. While it focuses upon antiques, it also does a great job with collectibles and art work, including folk art. It covers a lot wider range than just Maine. That may be the closest to an "industry" journal for this area that you can find. But, I'd look around to see if there are others. It is a fragmented niche. That's what makes it both difficult to explore and worth exploring.
I would also probably start exploring related niche markets to see how they interlap with the one that you are exploring. You may find your competitors exploring those areas, and these are related niches that you want to look at for your marketing efforts, too. You may find links to your competitors on the pages of these niche markets.
For instance, the Celtic music market isn't mainstream by any means, but there may be some overlap there that could be of value exploring. There are a number of forums and shops which focus on the music that may be nice partners, both for linking purposes, and for sharing referrals. Assuming those are good places to have a presence, which crafters, and craft stores are linked to on those sites?
I did a search on:
Found a lot of sites that may be competitors, and some that might be folks you might want to create relationships with. In addition to looking for links and competitors, you may want to find some communities that are interested in celtic arts and crafts. Those can give you a lot of insight into what people are interested in, and are looking for.
Here's one that might interest you:
There's a link to the Yahoo! discussion list at the bottom of the page, but this page includes links to a lot of potential competitors and partners.
As for conducting the competitive analysis itself, you've probably seen a page like this one from the SBA on competitive analysis, but if you haven't, it has a number of ideas that may be helpful to you in performing that type of analysis: