Re: Pink Floyd
Colonel Les Claypool's Fearless Flying Frog Brigade - Live Frogs Set 1 has a decent cover of "Shine on you Crazy Diamond". Also included is a cover of "Thela Hun Ginjeet" (from King Crimson's "Disipline" album), plus a bunch of Claypool/Primus/Sausage songs.
Speaking of Opeth covers... Their cover of AiCs "Would?" is great (easily my fav AiC song), its pretty straightforward and faithful to the original but good nonetheless. Also, their cover of Robin Trower's "Bridge of Sighs" is great (it got me to check out Trower). Oh and they also have an Iron Maiden cover, Remember Tomorrow, good too...
They're all pretty straightforward tho, I'd love to see them cover something and put their spin on it. Kinda like Carcass's remix of the Bjork song "Isobel", or APC's mashup of Love Song (The Cure) and Diary of a Madman (Ozzy).