Where to invest funds needed in 12-18 months

[HBFan]

I have a sizable chunk of money from a home sale.  I am currently renting and I am planning on building in the next 12-18 months.  I invest in the 4/25 with my retirement accounts, but I am not sure if that is a good idea for this period of time.  Right now I have it sitting in a money market account.  I would like to hear some others thoughts on what to do with this money until I need

[AdamA]

I have a sizable chunk of money from a home sale.  I am currently renting and I am planning on building in the next 12-18 months.  I invest in the 4/25 with my retirement accounts, but I am not sure if that is a good idea for this period of time.  Right now I have it sitting in a money market account.  I would like to hear some others thoughts on what to do with this money until I need

T-bills.

[KevinW]

Yeah, on that time horizon I'd just leave it in safe cash.

[cabronjames]

since it sounds as though you don't need it until at least Mar 1, 2013, you could put the first $20K by maxing out your 2012 I-Bonds & EE-Bonds, then sell the bonds when you need to after Feb 2013.

[MediumTex]

It seems like there are always good deals and incentives at banks if you open up an account with a large sum and leave it there for a certain period. 

I would look into some of these offers, since you have highly liquid funds and the luxury of not needing them for 12-18 months.