In trance music, the rythmic sounds are playing a prominent part in any tracks. Producers are always looking to innove with new sounds which could really make their track stand out. During the last years we have seen a strong trend for lo-fi sounds, also refered as bitcrushed sounds.
There are two ways of achieving this effect. The first one is simply to get samples that are already processed, and already sounds bitcrushed. While very simple, you will not really be able to modify / adjust the sounds as you want, and it can become a problem for the originality of your track.
There is simply no better than to "do it yourself"! There are many very good freewares out there that do bitcrushing.
If you produce with Ableton Live you are lucky because there is very good bitcrusher effect integrated by default with the soft. You can find it in the Browser, under Live Devices > Audio Effects > Redux.
If you don't work with Live and if your sequencer doesn't come with a bitcrusher by default, you can simply add one as a vst plugin. The one I would recommend is CMT Bitcrusher. It's a very simple freeware developped by students from a Finnnish university; it can be downloaded from
http://cmt.siba.fi/studies/Courses/2001-2002/VST/plugins/CMTBitcrusher/code/CMTBitcrusher.zip. There are 3 settings to play with: Drive, Bit-depth and Down Sampling