Data processing systems, user interfaces and methods are provided, which allow a user to select information sources, to rearrange associations between links to content items in the information sources and thematic information aggregations including the links and to access any of the information sources via the thematic information aggregation which contains the respective link. The user interface may be graphic, highly interactive, user-modifiable and zoomable, and implement elements of semantic analysis to allow the user arrange multiple content items from various sources into thematic information aggregations sharing unified interface, using only links to the content items. The thematic information aggregations may be synchronized across user devices and user statuses may be preserved.