As far as whole filler arcs, the list would be:
Warship Island Arc (Episodes 54-61)
Post-Alabasta and Goat Islands Arc (131 -138)
Ruluka Island/Rainbow Mist Arc (139 - 143)
G-8 Arc (196 - 206)
Ocean's Dream and Foxy's Return Arcs (220 - 228)
Ice Hunter Arc (326 - 335)
Spa Island Arc (382 - 384)
Little East Blue Arc (426 - 429)
Z's Ambition Arc (575 - 578)
Caesar Retrieval Arc (626 - 628)
Silver Mine Arc (747 - 750)
Marine Rookie Arc (780 - 782)
The Rainbow Mist Arc is actually pretty interesting for a filler arc with some decent level of world building, plus it leads directly into the next canon arc, so I'd advise watching it. The last few episodes of the Foxy's Return Arc lead into canon territory again as well, so I'd advise skipping through episode 227 until the character Aokiji shows up). I'd also advise just switching to the manga at some point, after the timeskip at the very latest, as whilst the anime does a good job at adding more emotion to it's scenes with excellent voice acting and music, pacing and animation take a massive decrease at that point.