Simile Timeplot and Simile Timeline from MIT SIMILE project Semantic Interoperability of Metadata and Information in unLike Environments are handy libraries to visualize time depending data.
ScientificCommons.org gathers now for more than 2 years data from several hundred repositories worldwide. That means that there is plenty of data for time series visualization. I just started to add graphs for the publication activity of each repository on the repository summary page. Here are some example pages: