Want to buy Treasury Bills and or Notes. Which ones?

Over the next 3 to 5 years I want to build up my fixed income holding. I'm not a fan of Mutual Funds for Fixed income. I was going to buy notes and or Bonds from Treasury Direct. If I'm going to be buying monthly what do you suggest I do?

I might suggest buying a 50-50 mix. I myself prefer t-bills, but there certainly can be a case made for having some notes, especially when the fed decides to give money away which they may very well do again when the housing market goes into the toilet. In that particular case one might even consider a few bonds but only a very few. Inflation and taxes are the curse of fixed interest paper. One might be better off buying bank stocks which tend to have increased dividends and earnings. But of course are subject to market conditions. BAC currently yields 4.5% for example. Darn close to t-bills and tax advantaged.

You could start to build a ladder of bonds/notes/bills maturing at different dates. On any Monday you can enter your order to purchase 3 month or 6 month T-Bills ($1000 minimum). At other times (see T-Direct schedule) you can purchase 1 year, 5 year or 10 year notes. (I'm not certain if they are still selling 2 year notes). Short term bills and notes protect you from rising interest rates; longer term notes protect you against falling rates.
Currently many people are betting that the rates will rise. If you believe that, then you would probably want to buy some shorter term instruments because purchases in the future would have higher returns.
If you were building a ladder with CDs, you would probably want to purchase 6mo, 1 yr, 1.5 yr, 2 yr, 2.5 yr, 3 yr, 3.5 yr, 4 yr, 4.5 yr and 5 yr CDs. Then as a CD matures, you would purchase a 5 yr CD. After some time, you would have a portfolio of 10 5 yr CDs, with one maturing every 6 months.