working with drupal project with team
Any control version tools: GIT, Mercury, SVN and etc for controlling team source.
Also drupal have prepared version of drupal installation for team working for tracking timelines, bugs, etc:
Drupal used as a project management tool
More version controlling tools reviewd here: http://www.smashingmagazine.com/2008/09/18/the-top-7-open-source-version-control-systems/

And there's many ready services (free or usually payment) for working with team in internet, try this search: http://www.google.ru/search?q=project+management, there I see basecamphq.com for example. 

More hard thing is DB synchronizing, because it's depend on your tasks, for example, sometime merging portion of content and users are needed, sometime aren't. Some of system variables should be synchronized, some of these not. Some content type or fields are required, some just for test.


Hard solution is writing script (manual) in any language that have access to DBs and track changes.
Other solution is using Features module with some contributed, like Strongarm and etc. This module create module that have changes, where developers export their changes, so it can be controlled via Version control tools as usual plain file. You will just enable it, and their changes will applied to central site. Also with this (and not only) cool tool used: Drush, for me this is the best solution. 
Also there's tools of synching depend on DB engine, Best tool for synchronizing MySQL databases for example.