Pari is a C library mainly for Number Theory, but it has excellent numerics, both real and complex case and with arbitrary precision. As it seems not to use much symbolics for that it is quite fast. This can be useful for some special functions or integration, see the appended example worksheets (and may be Linear Algebra a bit later these days).

I did that for matrix inversion:

Here is some stuff for doing that by calling Maple from Excel. The reason
is that one could care for extreme cases, where a really good precision
is needed. I included an example how to switch to rationals, where the
inversion can even be done exactly (do not use it for dimensions to high
and then it would be better to do it solely in Maple + cut&paste).

I did that for matrix inversion:

Here is some stuff for doing that by calling Maple from Excel. The reason is that one could care for extreme cases, where a really good precision is needed. I included an example how to switch to rationals, where the inversion can even be done exactly (do not use it for dimensions to high and then it would be better to do it solely in Maple + cut&paste).

To use it one must have Maple installed (I think at least version 8...

that location loads extremely slow - even using a very fast connection it may need over 20 sec to load (and with a modem it is sometimes messy ...)

it seems it had become slow over the last weeks

Occassionally Maple does not make me happy, if I want numerical integrals with more than the 14 digits which are supplied through the NAG librarys - that may be rather slow. So I wrote my own solution using LCC-WIN32 (a (free) compiler system allowing 104 decimal points of precision), where I coded the double exponential integration method. That gives me what I want to have in reasonable time. Details are sketched in the uploaded zip-file (it contains all what is needed to run the stuff). Some draw-back: this is for Windows only and because of OpenMaple at least Maple 9 is need.