Tough one. That's one of the reasons why I never moved to Linux. Too dependant on my PIM's that only exist on Windows.
As for todo list, I would have suggested PDesk with Progect, but on Progect group I have seen you requesting info on how to migrate to LifeBalance, so I think you are going the other way right now. PDesk is in Python, so I guess it should run on Linux, though the syncing probably not...not sure.
Chandler PIM from OSA Foundation is written in Python, thus shall run on Linux, the problem is it's still in alpha stage and lots of crucial functionality missing.
Mozilla.org has Sunbird and Lightning for calendaring.
Try remind:
http://www.roaringpenguin.com/penguin/openSourceProducts/remindThat's just a coincidental find though, I have no clue about time management apps on Linux.
Here is one collection:
http://linux.about.com/od/softpim/I would suggest considering to look at those web-based ones. Their independence on OS is probably their biggest advantage.
