Fruity Loops (there is a downloadable demo) is a well-known sequencer software that includes a lot of synthetizers, and is very suitable for beginners in electronic music production. At Youtube they are a lot of tutorial videos explaining step by step how to generate simple sequences and, the most interesting, these trance charasteristic synthetic sounds.
For example, this one: part 1, part 2, or this other one: part 1 - part 2 - part 3
