If you go to your network account page, you will notice that there is a "tagged questions" tab.
By default that page shows you two list of questions: "My Sites" and "Favorite Tags." The first list all the questions asked in the sites where you have an account, and the second list all the questions tagged with your favorite tags, asked in any Stack Exchange site where you have an account. If you are interested in other questions, or you want a list that include less questions, you can create a new filter. In the screenshot below, I have already created two filters.
If you click on "New filter," you will get a new page where you can set the criteria for the questions to be included in the filtered list.
You can add more than one rule, as I did with my filter.
Once you created a filter, you have also a RSS feed for that filter. The icon is visible in the bottom right side of the filter page.
The link has been changed to Filtered Questions. For the rest, what I said is still valid.