Drupal as feed aggregator I'm interested to aggregate posts on my Drupal site with the built-in feed aggregator.
The feed aggregator can make different feeds based on categories which is nice; my problem is that, when users create a post, they cannot assign a category at the same time. They have to later on find the post manually via the feed aggregator and set the category.

Is there a way to allow users to assign categories while creating a post?
The aggregator is for importing feeds from other sites, but it sounds more like you're trying to create new feeds on your site from your content. For that use, you could use Views.