Dark Matter Particle Candidates Dark matter appears to dominate the matter component of the universe as compared to luminous, or baryonic, matter. Though it does not interact electromagnetically (it doesn't absorb, scatter, or emit photons), there is an ever-increasing mountain of evidence for its existence through it's gravitational interactions with stars, galaxies, and clusters, as well as it's influence on objects behind it through what's known as gravitational lensing. 

My question is, what are the most promising particle candidates of dark matter, and which experiments currently exist (or will exist) to attempt to answer this question?
When you say "particle" candidates, I assume you're excluding MACHOs and RAMBOs. MACHOs are "dark" objects at the stellar scale like black holes, neutron stars, brown dwarfs, etc. RAMBOs are clusters of similar dark objects. MACHOs and RAMBOs are made of primarily baryonic matter (everyday stuff like protons and neutrons &mdash; electrons are not baryons but they can be a part of this too). 

This leaves us with the WIMPs and possible other particle candidates. I don't know the details of any experiments looking for these offhand (I'll see if I can find it out and update the answer in a few days), but the major particle candidates are:


Neutrinos: It's highly unlikely that these make up any significant chunk of the DM in our universe, but they deserve a mention.
Sterile neutrinos (I'm using the term in the specific sense here, not the general sense): This type of neutrino is right handed and only interacts gravitationally (note that there can be right handed active neutrinos, too). There is some preliminary evidence suggesting that these might exist.
Axions: These are hypothetical, but if they exist (and make up the majority of DM), we kill two birds with one stone by both explaining DM and resolving the lack f symmetry breaking in the strong interaction.
Gravitinos and the Lightest Supersymmetric Partner: Both of these require supersymmetry to hold, but they are major DM candidates.