Say I don't want to solve Rubik's cube but I want the reverse: I'm having a solved Rubik's cube (all stickers in it's right position and orientation) and I want to go from this state to a specific pattern. Are there any known algorithms for this? This is for a 3*3*3 Rubik's cube.
Set up the pattern you want. Solve it, writing down the moves you used. You now have a solved cube. If you undo the move sequence you wrote down, you will get the original pattern. In other words, if you invert the written move sequence (reverse the order of the sequence, and the turning direction of each move) you get a move sequence that generates the pattern you want.
Note that if the original solving sequence was optimal, then the generating sequence is optimal too.
This is in principle exactly the same as just solving the cube, but in practice it's much harder on the brain. Here's a way to do it that's kinda cheaty but demonstrates the equivalence.
You're starting with a solved cube. For each facelet of the cube, figure out where it needs to go. Look at what colour is in that place right now, on the solved cube. And then stick on an extra little sticker of that colour.
When you're finished doing that, every facelet has two colours: the original one and the colour of the place where you want it to end up. The original colours are solved; the new ones are jumbled. Now solve the cube using only the new stickers you've added. When that's done, the cube will have the configuration you want it to have.
 I don't know whether there's a standard term for this. I mean the locations where the stickers are, on a cube that's made with stickers. The things there are 3x3 of on every face.
Doing this without defacing your cube with extra stickers is difficult because there's a lot to keep track of mentally. Jaap's approach is easier, if you already have a way to get the cube into the configuration you're aiming for and are just looking for a more efficient way of getting there, but if the problem is that you don't know how to get that configuration at all then you need something like the procedure I've described.