I came across this image on pinterest last week and now I'm completely enamored with bottle brush Christmas trees.  I don't have a collection yet, but I think i might have to keep my eyes open.  I may have something new for the mantel next year.
Here, someone has amassed quite a collection
I love all the color
And the ones without color too!
And the ones that are flocked and have their own ornaments are beyond sweet
I've read grumblings that I could easily pick up a few at Michael's or Hobby Lobby that could be turned into something.  Maybe if I'm feeling crafty (oh, holiday knitting, will you ever be done???) I might try to create my own magical forest....they do look so cheery all grouped together. 
ETA: apparently I have the start to my collection already!  I just went downstairs and look what was sitting on the mantel