Feeds are a powerful and popular means of staying updated and they are also powerful distracters on a blog. If you have feeds to other blogs or news sites (like I have), it would be a good idea to use the code given below. If you are new to HTML etc just make sure you backup your template before proceeding with this hack.
Depending on the number of feeds you have in your blog, blogger names each feed widget as Feed1, Feed2 etc. To find out the blogger-assigned name of a particular feed widget, just hover your mouse cursor over the edit link of that widget in the layout -> page elements section of your blogger account and in the browser’s status bar you will see a link with the blogger assigned name a.k.a the widget ID.
However, this exercise may not be required if you have assigned a title to your feed widget. You can search for a particular feed widget’s code in your template using its title or the widget ID. Once you have located the feed widget you wish to modify, you should look for the following code in there. Look for the line which goes <a expr:href='data:i.alternate.href'… and add a target='_blank' to it and you are done. Simple isn’t it?
<b:widget id='Feed2' locked='false' title='Reuters: Top News' type='Feed'>
<b:loop values='data:feedData.items' var='i'>
<a expr:href='data:i.alternate.href' target='_blank'>
I have applied this hack only to third-party feeds in my blog. If you are using your own feed to display recent posts etc this may not be required as even if some one clicks on a link in that feed widget, they remain on your blog.
As always, if you face any problems, just drop a line here and I shall look into it. Also note that this hack is only for blogger beta blogs.