In a recent answer, KRyan mentions that there are multiple tricks to get infinite caster level in 3.5. I'm not aware of very many, and those I am aware of require iffy rules interpretations:
- Greater Consumptive Field (SpC, p. 51) does not work on its own (even with a permissive reading of the spell, it caps out at twice your unimproved caster level). However, alternating castings of Greater Consumptive Field and Consumptive Field will work if you read "your original caster level" to mean "your caster level before you increase it with this casting" and not "your caster level before any temporary increases."
- The other high-impact caster level trick I'm aware of is combining Ur-Priest (CD, p. 70) with Sublime Chord (CA, p. 60) to exploit their non-standard caster level calculations. This trick was popularized by the early optimization showcase The Wish and The Word. However, I believe this trick requires conflating "caster level" with "levels in spellcasting classes," and therefore doesn't actually work.
What other tricks exist to achieve infinite or extremely high caster levels (say, caster level >100 at character level 20)? Which ones require permissive readings of the rules, and which are more airtight?