For portfolio, you can use any embedded project: site visits, the bot users, the game players, etc.
Now, most of the complexity of software development is not writing the code, and in related activities (research, organization of the environment of development, testing, implementation, support, etc).
Therefore, the project with the users (personally, in my eyes) will give odds to more complex project is developed "on the table". Therefore the main recommendation is to solve a specific task, and not to fantasize. If there is an article on some habré with likes and comments, very good.
Design projects can come in both plus and zero, depending on how interviewing for a large aware of the topic on which they were made.
Recommend the more precise the topic is difficult, because it does not specify what exactly you want to do (in any field at least: web, machine learning, offline software, etc).
The site only projects with no special meaning. It easily replaces the profile on github. If you make a website, a blog, that it was some useful materials. Early in his career, on a personal blog good articles do not write a lot, so better to go, again, in any Habr.
That is, it turns out that in the summary (first), better to put the links to github and profile Habra, than a personal website.
The entire stack will not prompt, but employers distinguish and appreciate good skills in LINQ , can feel free of him alone to write.