People who've kept up with Smallville for the last 3-4 years...?

So, I watched Smallville a LOT in high school, but then it started getting switched to time slots that were conflicting with my schedule, and I managed to watch most of season 4 (and still have it on VHS, cause I had to tape it) and sort of lost track when I went off to college, which was season 5 I believe.

Anyways, back to the topic at hand, what season is Smallville currently starting? Are the episodes between about halfway through season 5 and now all one continuous arc, or are there 'filler' episode that can be skipped without missing any important plot points? If so, what episodes are 'filler' and what ones have important stuff happening in them?