I've been using a box of Miracle-Gro I got at a huge discount 4 years ago. It's not the best fertilizer out there, but it does make most of my orchids bloom and my foliage plants go crazy.
I also like to mix into my irrigation water a little magnesium sulfate (epsom salt) and SuperThrive. The MgSo4 helps plants photosynthesize more efficiently and who knows what the SuperThrive does! I've been meaning to do a small controlled study on it to see if it has any actual benefits.