Taxi Crew missions are very important to change Soyuz ship every 6 months. Russian Soyuz is the only way to escape the ISS International Space Station in danger case and it is indispensable to have this ship in perfect conditions every time.

For all news, images, Soyuz TMA reference and more, click HereFirst Crew arrived to the ISS with a Soyuz and
three successive Taxi Crew missions exchange these ships leaving the new Soyuz
docked to the ISS and returning to Earth with the old one (6 months old).

Here you can find info about first 3 Taxi Crew
missions and incoming 4th to the ISS:

4th  
Taxi Crew to ISS - Soyuz TMA-1
Oct. 30, 2002 - Nov. 9, 2002

Commander
Sergei Zalyotin
Belgian
Flight Engineer
Frank De Winne
Flight Engineer
Yuri Lonchakov

Crew's info and images here at SpaceOnLine WebSite:
4th
Crew