I've saw that i have 3 folders under /lib/modules path:
2.6.28-omap1
2.6.28.10-bfs10
2.6.28.10-power53
current

uname -a ------> Linux Nokia-N900 2.6.28.10-power53
So as i'm understand right i'm using kernel-power

Running the next command:
ls -l /lib/modules/current
Shows me:
/lib/modules/current -> 2.6.28.10-bfs10

du 2.6.28.10-bfs10 -----> 8652(about 7.3 megabytes)

Do i really need this kernel that takes so much of my NAND?

No. 10 chars