SEOSpyglass, but I have my own questions about its accuracy

seo spyglass and yahoo site explorer are the best ones

BacklinkWatch.com is free, web based and good in my opinion. SEO Spyglass is also excellent - even the free version is great.

Do you try using backlinkwatch, its an effective tool base on experience.

I disagree with the guy who said G's webmaster tools. They show very incomplete results and take a long time to show up.

Personally I do a combo of y site explorer (search site:http://www.site.com) and SEOSpyglass.

I personally use tools from seocentro.com and submitexpress.com when I'm checking the number of my backlinks. You can check it out for more tools.

A tool I find to work well is Link Diagnosis - examine your link competition (also has a FF addon to make it all work nicely) as well as Majestic SEO for tracking backlinks and such.

Def give Linkdiagnosis a shot as you can check others BLs out without having to pay or own that site.

Download the seo toolbar for firefox. I think it uses data from yahoo site explorer for backlinks, but it is quick and easy.

I use a combination of Majestic SEO and SEOSpyglass. Majestic SEO checks backlinks for a website you can validate for free, and it charges fees (pretty high ones) for the rest.

Spyglass is inexpensive, but the results are quite accurate - I use it to check backlinks from the websites I don't own.

Try SEOSpyGlass. Download free version of it with less features but you can get your competitors backlinks report and you can also check keyword rank of your website.