Which Naruto Shippuden filler arcs are safe to skip, and are any worth watching?

The reliable approach: follow a canon episode list (any up-to-date filler guide works) and apply these overrides:

Skip freely: the long mid-series filler blocks (Three-Tails arc, most of the Past Arc reruns, the ninja-ostrich-tier one-offs). Nothing canon hides in them.

Filler worth watching anyway:

• Kakashi ANBU arc (episodes 349–361) — technically anime-original but adapts supplementary canon ideas; widely considered the best filler in the series and genuinely enriches Kakashi and Yamato.
• The Itachi Shinden episodes (451–458) — adapted from the canon novels.
• A handful of aftermath episodes near the end that adapt novel epilogue material leading into Boruto.

One warning: during the War arc, filler is spliced into canon episodes rather than cleanly separated — a mixed-episode guide saves you from either sitting through infinite Tsunade flashbacks or accidentally skipping a real death. With smart skipping, Shippuden is ~330 episodes of actual story. Perfectly doable.