Class C IP's: Does it Matter?

Hi friends,

I'm new here and I was just wondering if I should different IP's
whenever I build links (and should those IP's all be class C)?

If differing IP's are beneficial, is there a place where I can get them
for free? Recommendations wanted.

/bump I would also like to hear about the effectiveness of using individual class C ip's from someone who knows what their talking about.