You need to have backupmenu from the extras-devel repository installed to export all of the partitions to the PC via USB. Here is what i would suggest. Here is a walkthrough for those steps :

Install Backupmenu to your N900
Reboot the N900 with keyboard ejected
In Bootmenu type 'w' to export the partitions in read/write-mode
Boot your PC from the Live-CD
Start gparted
Choose the device (hard disk) in the upper right drop down menu should be some 30GB size.
Right click the first partition (approx27GB) and choose 'Resize or Move', use the right handle to shrink the partition.
Click 'Resize'-button (Dont worry you will be asked to apply actions later)
Right click on the second partition (approx.2GB) and choose 'Resize or Move', use the left handle to fill the free space created by the first resizing.
Do not touch the third, aka swap-partition.
Now click apply in the upper toolbar and accept the changes to be applied.
If everything is resized successfully, shut down the PC
On the N900 press 'q' to quit backupmenu and restart Maemo.

You might want to read about it here http://talk.maemo.org/showthread.php...16#post1136816

Do not panic if the first attempt fails, because of the stale file handle error. It may happen that the default file system check, that gparted will try, errors out.
Open a Terminal on your PC and try to run the file system check from that. For Ubuntu that might require for you to identify the partition name in gparted gui. Then first Yes, sir, do it twice! The XYZ must get changed to the identifier from the gparted gui. If you still get errors please tryIf no more errors will put out, follow the procedure to resize the partitions from the above link.