well im not going to do a huge master list, but i can give my two cent's worth. They will probably be ones that you already knew
On the earlier albums i have no idea who does what solo.
On still life, Mike does the solo to Godhead's Lament and serenity painted death, while in White Cluster they are duelling guitar solos,
Mikael does the main solo on The Leper Affinity, but Peter does the sort of mini-solo with the sweep arpeggios. Mike also does the solos of bleak, harvest, the drapery falls. i think peter does the main solo of the funeral portrait, and he definiitely does the one on Blackwater Park.
I think mikael does all of the solo's on damnation.
I havent listened to deliverance enough to know exactly who does which solo, however peter does the first solo on the song deliverance (i personnally find this to be opeth's weakest solo) and mikael does the second solo.
I think that most of the solo's on Ghost Reveries were mikael's, the only one im sure peter did was the cazy one at the end of beneath the mire.
and i'm not even going to get into watershed because i think it's pretty obvious which player plays which solo.
It's especially easy to tell peter and mikael's solos apart. Mikael has a very smooth, flowing traditional soloing style. While Peter plays very choppy solo's that i find don't always sound to good. for example, the solo in deliverance sounds like peter took parts of 5 solo's from very different songs and pieced them all together. I'm not a huge fan of this style. also i find peter picks too hard.
Anyways, there's my contribution, add stuff on if you know any other ones.