I have really good experience with free package Syrup for Maple. It can symboliclly evaluate all currents and voltages in circuit (ac, dc and tran analysis), from enetered spice netlist. It was enough for my problems. Here is download and examples link:
**broken link removed**
**broken link removed**
For more complex circuits, solutions can become too large, and some sort of simplifications should be done. For example 1/gm<<rout, which alows 1/gm to be neglected in the sum. Also user could specify such conditions for some other circuit parameters. ISAAC is comercial package for mathematica that has such functions, but in my opinion too expensive, because it is not stand alone program...
Tina Pro has schematic capture and is also interesting.
Here are some symbolic simulators for which I have heard, but not used:
ASAP, SYNAP, SAPEC, SSPICE, SCYMBAL, SCAPP, GASCAP
For more information, you can read chapter 32 of the book Trade offs in analog circuit design: