Connected Papers present graph of papers that are similar to each other. However, note that this is not a citation tree. Each paper is a node and there is an edge between papers if they are similar. The similarity matrix is based on co-citation and co-references.
The node’s colour represent the publication year and the node’s size correspond to the number of citation. The graphs are built on the fly given a link or title.
The interface presents the papers’ abstract which makes it easier to browse and jump between the different graphs.
Two small features I can think of is to filter papers according to a publication year and an option to download citation (i.e. bibtex, APA).
I believe that I’ll used it extensively when working on related work.