Can you point me to examples of interesting scientific posters featuring results of geospatial analysis and/or geovisualizations?
Most GIS scientific posters will come out of either Universities or State GIS conferences. Here are two examples:
Look on http://wiki.osgeo.org/wiki/FOSS4G_2009_Posters for some examples. Unfortunately, I don't found posters examples for the FOSS4G 2010.
Maybe you can try to browse on FOSS4G conference pages. They usually have poster session, like this one FOSS4G Europe 2015.
May I add this website that ESRI has their Map Book Gallary. It has Online, Map Book archive ? Sometimes when I need something to look at, I usually go this site and to look at them.
There is another one not only for International but in United States as well..