Have you been using anchor tags leading back to your website?

Yep....I use anchor texts when I can. Sometimes the author name on some of the blog and forum comments carries the link back to the site.

I would suggest that you should look again with your previous activity, maybe you may overlooked something with your link building process and creating your story or there's something wrong with your content, analyze what you've done for you to realize what's the missing piece. hope this helps.

It can sometimes take a while for them to show up in Yahoo Site Explorer...even then it's not always real accurate. Don't worry about it. Just keep building back links consistently and you'll see the results.

Like others have said, sometimes it is a waiting game..However, if you have a url list of where each of your links reside, then you can give them a nice shove in the right direction by using a backlink indexing setup.

Cheers

In order to see if those backlinks have been indexed by google, Search for a non spun sentence in your article in quotes. It should give you a good idea of the number of indexed articles. For instance if I had a non spun phrase like : It's probably originated from the late 20th century, when people were astounded with the sky.

I would do a search in quotes on google like "It's probably originated from the late 20th century, when people were astounded with the sky." and look at the number of results.
You need to understand that yahoo explorer or any other backlink checker do not show you all the backlinks pointing to your site.

Thanks everyone for your help. I will just be patient and continue to build backlinks and see what happens.

Yahoo takes a long time to crawl the web...and yahoo/google could be ignoring some of your 1000 article sites as they are probably junk/spam sites

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What tool are you using to check the backlinks?

This is one thing that you need to learn how to be consistent at and learn how to be patient. Honestly