SWIM has a ritual with LSD and weed.
A medium-strong dose of LSD is taken, either after a good bowl (daily pothead...) or before a smoke has been had for the day.
It's important to get the dose of acid right. This works best when you have taken enough to cause overt open eye visuals, but not enough to start getting seriously lost while peaking.
Before the trip, SWIM has been reading a bit and watching things that interests him (documentaries, nature shows, etc.) These are the things that will program your trip, so choose them carefully.
The trip should be fun and engaging, but not overwhelming. Usually it is nice, sort of clear headed and ethereal.
Around the fourth or fifth hour after dosing, a good sized bong hit is taken. This causes an almost immediate plunge into the underworld.
The trip hits you like a train, and now you are deep in some shit. If everything has been executed properly, you should be connecting to the vast, gaiaan folds of knowledge, otherwise known as the tree of life. This connection is made easier by the addition of some kind of input. I usually like to put on a good nature documentary, and get lost in the worlds of insects and plants.
I'm pretty sure you will 'fuse' with whatever media input you take choose at this time. Movies, music, art, probably even a book if you read enough.
This method is hard to perfect, and as far as I know it only works for SWIM, but it is one of his favorite drug combinations. When used correctly with LSD, cannabis adds a dimension to the experience that is quite difficult to get from LSD alone.
Some other good acid combos:
Mescaline - beautiful synergy.
Poppy pod tea - at the end of a trip, this can be amazing. It adds a lot, reduces anxiety, and completely changes the visuals. One of SWIM's only experiences with lucid dreaming has been a result of this combo.
DMT - extends the spice, and in SWIM's experience, requires a little more for a full effect. The full effect is quite a bit more of an effect though... Only gave this one an earnest try one time.