  We discuss the prospects for detecting supersymmetric particles in variants
of the minimal supersymmetric extension of the Standard Model (MSSM), in light
of laboratory and cosmological constraints. We first assume that the lightest
supersymmetric particle (LSP) is the lightest neutralino chi, and present
scatter plots of the masses of the two lightest visible supersymmetric
particles when the input scalar and gaugino masses are constrained to be
universal (CMSSM), when the input Higgs scalar masses are non-universal (NUHM),
and when the squark and slepton masses are also non-universal and the MSSM is
regarded as a low-energy effective field theory valid up to the GUT scale
(LEEST) or just up to 10 TeV (LEEST10). We then present similar plots in
various scenarios when the LSP is the gravitino. We compare the prospects for
detecting supersymmetry at linear colliders (LCs) of various energies, at the
LHC, and as astrophysical dark matter. We find that, whilst a LC with a
centre-of-mass energy E_{CM} <= 1000 GeV has some chance of discovering the
lightest and next-to-lightest visible supersymmetric particles, E_{CM} >= 3000
GeV would be required to `guarantee' finding supersymmetry in the neutralino
LSP scenarios studied, and an even higher E_{CM} might be required in certain
gravitino dark matter scenarios. Direct dark matter experiments could explore
part of the low-mass neutralino LSP region, but would not reveal all the models
accessible to a low-energy LC.
