Matlab/Simulink is provided by The Mathworks and is generally only available from approved Matlab distributors - these typically are university libraries, and dedicated scientific software distibutors.
Depending on your needs you could always look at a Matlab alternative like Octave or FreeMat, both of which are free.
On this note, is EWB a piece of crap for simulation? Or do I just not know how to set the transients if it aborts even the simplest 555 simulations within a minute or two.. If I set giant timesteps, the simulation time is greater when aborted, but probably with nearly the same number of iterations as when I use 10^-5s default values, and the simulation aborts only milliseconds in..
I've tried tinkering all over, even adjusting circuit values.. It just enjoys crashing it seems.. I'd be very happy to find out that I've overlooked something embarassing..
I recommend this. It also has a simulink-like component but requires visual studio on Windows (problematic) and gcc on Linux (easy).
There are many other Spice programs out there. Very few are compatible with one another. If you need Pspice, there's only one place to get it. If you need something general, try LTSpice, ICAP or gEDA (difficult).
Regarding EWB, I've always had convergency issues and the dreaded "timestep too small" error dialog.. however version 10 includes an automated assistant that tries different configurations to solve the problem, and suprisingly it works! So I recommend updating..
It was multisim's convergence issues that drove me away. That and they wanted about what I paid for the original EWB to "upgrade" to multisim.
Since my move to TINA, I've haven't looked back. Any problems I've had, I just inform the designers. The free version is called TINA-TI and is at the Texas Instrument's website.