You want to link to as many pages from the home page as possible. Gary makes a good point that people do think they have to choose a child menu item when they see a dropdown.
But as a SEO point of view drop downs are fine. And as I said get as many pages linked from the home page as possible
http://perthseocompany.com.au/seo/tutorials/a-simple-explanation-of-pagerank

So,thing else, i noticed in your site. you have 90+ pages with 2 canonical tags, here is an example.

this will not be helping

http://www.marketing91.com/marketing-bookstore/

It must be the root of the problem as the offending links have "linksalpha.com" in them.

http://www.linksalpha.com/social?blog=Marketing91.com&link=http%3A%2F%2Fwww.marketing91.com%2F6-marketing-lessons-harry-potter%2F&title=6+Marketing+lessons+from+Harry+Potter&desc=1+Have great quality+– +No+one+can+argue+this.+The+Harry+Potter+series+(along+with+lord+of+the+rings)+is+one+of+the+best+books+I%2C+and+many+others%2C+have+read+till+date.+Quality+is+all+it+provides+&fc=333333&fs=arial&fblname=like&fblref=facebook&fbllang=en_US&fblshow=1&fbsbutton=1&fbsctr=1&fbslang=en&fbsendbutton=0&twbutton=1&twlang=en&twmention=marketing91&twrelated1=&twrelated2=&twctr=1&lnkdshow=noshow&lnkdctr=0&buzzbutton=1&buzzlang=en&buzzctr=1&diggbutton=1&diggctr=1&stblbutton=1&stblctr=1&g1button=1&g1ctr=1&g1lang=en-US

I believe this is your problem, this plugin for WordPress.

http://dev30.linksalpha.com/?p=8