This is very easy and you do not even need any external code.All it requires is your site have a feed url.If your are on the default blogger feed your feed url will be
http://youblogname.blogspot.com/feeds/posts/default
If you are on feedburner then your url will be something like
http://feeds.feedburner.com/xxxxxxxxxxxx
okay now here is what to do.
Go to the page elements section and select add gadget
Select feed
Enter your feed url
Customize it the way you want and then change the title to recent posts or something like that
That is it and you are done.
NOTE:You can also do this with comments just change the post feed to your comment feed
