Ds (5) went to Montessori last year, but now we hs/unschool.
As different as Montessori and Waldorf seem to be, they are really quite compatible. Montessori seems to appeal to a child's innate love of learning while Waldorf celebrates the magical qualities of chilhood. I believe both are important.
Some of our favorite Montessori ideas:
Providing smaller versions of everyday objects (like brooms, apple slicer, water pitcher)- they should be usable and not just for play.
Keeping toys, etc on shelves rather than boxes/bins.
Making common items (snacks, toothbrush, coathook,etc) accessible.
Encouraging participaton in everyday tasks (baking, chores,etc).
Keeping your living space orderly
The Montessori classroom is mixed, this is also a hs philosophy as associating solely with our peers is very unnatural. Also, many materials are self-correcting which I can correlate to unschooling. We don't actually use any of the materials, but I know T.C. Timber has a lot of cool Frobel (sp?) stuff- basically advanced wooden educational toys.
Many of our Waldorf practices stem more from our spirituality and values. Celebrating the seasons, natural materials (although this gets harder as they get older- playmobil and legos seem to be taking over!), songs, rituals, creative play, etc.
Both stress media-free is the best way to be!
I hope this helps and that I didn't babble too much!
Read as much as you can.