I think Miller is available for the LLE and that he will most likely get that. Small chance he is available for a minimum contract.
I've seen a couple of teams linked to him already. The most serious of those seems to be the Houston Rockets. Appearently, Adelman is pushing hard for him + Houston want a 20-25 minute a night legitimate center so that they can bring back Yao slowly.
Cs don't have the LLE to use (since it was used last year on M. Daniels.
I think folks have an outdated idea of what it costs to sign a decent backup center in this league.
Backup centers who recently signed contracts (I got this from the shamsports site, and stopped after the Detroit Pistons):
Zaza Pachulia (4 years $19M, 2009)
Nazr Mohammed (5 years full MLE, 2006)
Desagana Diop (5 years full MLE, 2008)
Varejao (6 year $48M, 2009)
Chris Anderson (5 year $21M, 2009)
Kwame Brown (2 year $8M, 2008)
Ben Wallace (1 year min, 2009)
Fabricio Oberto (3 year $11M, 2007)
...
You get the idea. Anyone looking to sign Miller is looking at spending probably close to $4M per year. Miller will have fewer good years left, so it will be a shorter contract -- probably similar to Oberto's. If the Cs could sign Miller to a 2 year $8M contract, it would count as a bargain.
Now (1) some might object to the idea that Brad Miller counts as a "decent" backup center, but don't fool yourselves too much. He is decent&serviceable, but not great.
(2) Ben Wallace was available cheap last year. But that's about it on the list. If he's willing to do that again, and do it for the Celtics, then great, let's get him.