GeoApt Spatial Data Browser
From Wildsong
So new it does not even have a name yet.
Adding MrSid support
Adding MrSid to GDAL: complete instructions for Ubuntu
http://trac.osgeo.org/ubuntugis/wiki/UbuntuGISRepository
As part of this process I added the "unstable" GIS repo and updated all my existing GIS packages to the latest versions.
I had to become a LizardTech developer to download the SDK. If you want MrSid support, you do too.