  Type Ia supernovae (SNe) are the best standard candles available today in
spite of an appreciable intrinsic variation of their luminosities at maximum
phase, and of probably non-uniform progenitors. For an unbiased use of type Ia
SNe as distance indicators it is important to know accurately how the decline
rate and colour at maximum phase correlate with the peak brightness. In order
to calibrate the Hubble diagram of type Ia SNe, i.e. to derive the Hubble
constant, one needs to determine the absolute brightness of nearby type Ia SNe.
Globular cluster systems of early type Ia host galaxies provide suitable
distance indicators. We discuss how Ia SNe can be calibrated and explain the
method of Globular Cluster Luminosity Functions (GCLFs). At present, the
distance to the Fornax galaxy cluster is most important for deriving the Hubble
constant. Our present data indicate a Hubble constant of H_0=72+-4 km/s/Mpc.
  As an appendix, we summarise what is known about absolute magnitudes of Ia's
in late-type galaxies.
