I can't vouch for the quality or the safety of this recipe, since I haven't tried it (and probably never will), but English Russia has a how-post on making your own absinthe. There are a lot of herbs involved.

Wormwood: 100 g
Fennel (fruit): 50 g
Anise: 50 g
Mint: 15 g
Melissa: 8 g
Chamomile: 3 g
Cumin: 10 g
Angelica: 10 g
It would be nice to add 5-10 g of hyssop, but it is difficult to find.

And then later another round of herbs.

Melissa: 8 g
Licorice: 10 g
Mint: 15 g
Chamomile: 2 g
Angelica: 2 g

One of the steps is to put the concoction away for two weeks, presumably to give you time to ponder the wisdom of the whole enterprise. Link -via Dangerous Minds