With blogger make sure your blog settings are set to ping and that "let search engines find your blog" is turned on... And use pingomatic(dot)com on top of that. Also, make sure you are listed in technorati.

Personally I prefer to have my blog on my domain... and just not do anything that would harm the rest of my site (ecommerce, etc) Otherwise I feel like I'm just promoting another company's domain (no matter how much I like them)

__________________