I am a big proponent of i-bonds held at the US Treasury via treasurydirect.gov. You can buy $10K / year.
I-bonds are the world's best relative value in fixed income. They are TIPs that don't have duration risk or any mark to market risk since they are not a security. No credit risk either. I use them as my emergency fund and also consider them my bond allocation.
Interest/Coupon:
nominal rate ( currently 0%) + official inflation rate
Liquidity: None in year 1 (locked in), 3 months interest penalty in yrs 1-5, no penalty thereafter
Term: 1-30 yrs (you can hold them for up to 30 yrs).
Taxation: deferred until redemption
After year 1, this is "inflation linked cash". They earn a pre-tax real return of 0% with no duration or credit risk; this is very good in today's bond world. They are both an inflation hedge and a deflation hedge because their principal can never go down; unlike a seasoned TIP you can't lose principal and interest if deflation happens.
http://blogs.wsj.com/wallet/2008/12/12/how-deflation-would-affect-tips-and-i-bonds/New issue 5 yr TIPs yield about 0% so almost the same as i-bonds, but they have a little more duration (since the principal payment is 5 yrs away, rising interest rates would still affect them a little, and worse tax treatment.
I also don't need more emergency savings than what I already have built over the past few years with the $10k/yr limit.