Here's a list of regen trinkets. I omitted most 346 trinkets as I'm not really interrested in them.
I used Danner's regen calculator to calculate mp5 values for intellect and spirit. I used 4500 int and 2500 spirit as base values and a 300 second fight length.
The values will vary with your actual spirit and intellect, so don't use the values I give as absolute truth. They're just there to have some metric to compare the trinkets between each other.
Blood of Isiset - Halls of Origination
285 mastery, 1710 spirit proc (15s / 90s ICD, about 16% uptime). This averages out to 285 spirit.
Total regen: 403 MP5
Notes: The mastery can be reforged to get more spirit, if you need even more regen.
Tear of Blood - Stonecore
285 intellect, 1710 spirit proc (15s / 90s ICD, about 16% uptime). This averages out to 285 spirit.
Total regen: 636 MP5
Notes: Definitely the BiS pre-raid level trinket as far as regen is concerned.
Mandala of Stirring Patterns - Exalted Hellscream's Reach / Baradin's Warden
321 spirit, 1926 mastery proc. (no data, but I assume it's 16% uptime like the others, averaging to 321 mastery)
Total regen: 454 MP5
Notes: Pretty weak for regen, pretty weak for throughput. Not really worth the rep grind...
Tyrande's Favorite Doll - Archaeology
321 intellect, 4200 mana / 1 min on use. Averages to 350 mp5.
Total regen: 612 MP5
Notes: Gives slightly less regen than tear of blood, but offers slightly more intellect. Also, be prepared to spend a lot of time grinding archaeology to get this one...
Core of ripeness - Valor points
321 intellect, 1926 spirit for 20 seconds on a 120s cooldown. 16.67% uptime so about 321 spirit on average.
Total regen: 717 MP5
Fall of Mortality - Cho'gall
321 intellect, 1926 spirit for 15 seconds. Looking at some logs it looks like 16% uptime, so 321 spirit on average.
Total regen: 717 MP5
Notes: This and core of ripeness are basically exactly the same. The valor point trinket has the slight advantage of being able to time the spirit use with a mana tide for bigger returns.
Darkmoon Card: Tsunami - Inscription
321 intellect, 80 spirit stacking up to 5 times. 400 spirit on average if the stack never falls off.
Total regen: 829 MP5
Jar of Ancient Remedies - Maloriak
103 spirit stacking up to 5 times. The stack can be consumed every 2 minutes, returning 6420 mana. Prevents it from stacking spirit for 30 seconds. To model this, I assumed a 75% uptime on the spirit stack + 6420 mana return / 2 minutes.
Total regen: 814 MP5
Notes: While this trinket returns about 100 more mp5 than core of ripeness and fall of mortality, it doesn't offer any throughput at all, like the other trinkets do.
Fall of Mortality (Heroic) - Cho'gall Heroic
363 intellect, 1926 spirit for 15 seconds, assuming 16% uptime averages to 321 spirit.
Total regen: 751 MP5
Notes: It seems strange that the spirit proc is the same as the normal mode version. The uptime might be better for the heroic version, but I don't have any data.
Jar of Ancient Remedies (Heroic) - Maloriak Heroic
116 spirit stacking up to 5 times. The stack can be consumed every 2 minutes, returning 7260 mana. Prevents it from stacking spirit for 30 seconds. To model this, I assumed a 75% uptime on the spirit stack + 7260 mana return / 2 minutes.
Total regen: 918 MP5
Shard of Woe - Sinestra (Heroic only)
Reduces base mana cost of spells by 405. 1935 haste on use for 10s / 1min CD.
Total regen: 1012 MP5 (30 casts / minute), 1350 MP5 (40 casts / minute), 2025 MP5 (60 casts/minute)
Notes: Not sure on the math for this one, I simply multiplied the amount of casts by the mana reduction to get a total mana reduction.