Login to your Google webmaster account and inside "Links to your site" you will find total no. of sites links to you.
Yes, it is the easiest way to check your sites' backlinks. Of course, if you want to gain more detailed information about backllinks, you'd better check it in Google Webmaster Tool.
There are several method to check your site back link : You can open the yahoo explorer and puts your URL and see your back link in your sites.You can also see Google webmaster account.
There are thousands tools online. Just google "Backlink checker" without quotes (or you can write with them, but you will gain less websites)
The old Google trick is inaccurate and outdated, even the Google Webmasters "links" feature is behind. Yahoo is probably the best for link exploring. Also, if you have stats lookup on your server, you can also find some of the most high impact links that are getting through.
Google won't show you all your links. Yahoo is more accurate. Also you can goole for services what provide backlinks checking, but almost all of them use Yahoo's data.
But the problem is backlinkwatch works with only 50,000 queries a day. You have to be lucky for the day.
You can check without space on Google, but google is not shown all back links, if you need all back links then check at yahoo site explorer or backlinkwatch.
Your views on this topic are really interesting and informative, but i can't understand how can yahoo explorer work.
Search in Google for back-link checker tool.You will find many tools to check your actual backlinks with other factor like is it a do follow link and how many outgoing links are on that page.