I have been using this week, a software called Comment Sniper. It is one of the best software that i have downloaded lately.
What is Comment Sniper?

Comment Sniper is a free software that allows it’s user to keep track of new posts of your favourite blogs. You just add the desired blogs to the tracking list (i have around 10 so far), choose the scanning interval (i use 5 minutes), and the software will alert you with a small popup on your lower right screen corner, every time it detects a new post on any of the blogs you added to the list.