It is time to start tracking the yield on tax-exempt money market funds. Interest rates have started inching up lately, causing the net asset value of municipal bond mutual funds to fall.
Things are pretty early in the rise though. The yield on the Vanguard tax-exempt California money market fund [VCTXX] is still a miniscule 0.12% as of December 8, 2010. This yield is actually a lot higher than the Vanguard prime (0.06%) or Federal money market fund. (0.01%)