QUCS is alright. It does verilog-a, I think it can load SPICE files, has a decent parts library, enables parametric plotting of circuit parameters, can do basic transmission line and PCB layout simulations, etc. I found “A Qucs Tutorial for RF” helpful for getting started; the default tutorial is also good.

On debian wheezy, install the following (some are probably not necessary, like cmake):

sudo aptitude install libxml-libxml-perl libgd-gd2-perl zlib1g zlib1g-dev libgd2-xpm-dev libxml2 libxml2-dev libxml-perl libqt4-dev libqt4-qt3support automake libtool gperf flex bison cmake

Then follow the build directions at https://github.com/Qucs/qucs/wiki/Build-Linux. You don’t need to set the --prefix, but you do need --enable-maintainer-mode. You probably want to make -j8 to build faster.

Within QUCS, one “gotcha” is that simulating only creates a simulation engine and dataset; you then need to go to (or create) a data pane (seperate sheet from the circuit schematic) to visualize the results.