Is there a reasonably complete collection of ways for casters to overcome spell resistance?
The most reliable method of overcoming SR is to use spells that bypass it. You can use d20pfsrd.com's spells DB to filter out all spells that require a caster level check when they encounter SR, or look for "Spell Resistance: no" in the spell descriptions. Conjuration spells are especially good in this area.
As others have mentioned, buffing the party is often a good way to contribute without having to beat SR. (But note that unless they drop their SR as a standard action, allies with SR will still block applicable spells.)
Extraordinary and supernatural abilities are not affected by SR. For example, most hexes do not require caster level checks.
Finally, there was recently a thread on this subject in the Paizo forums for increasing spell penetration for those situations where SR checks are required. Cao Phen in particular provided a wonderfully comprehensive answer. Here I've copied his list, added a handful of additional niche options, and provided links to the SRD.
- Elf: +2 vs. SR
- Human, Cleric favored class: +1 vs. SR (outsider targets only)
- Tiefling, Cleric favored class: +1 vs. SR (outsider targets only)
- Dhampir, Wizard favored class: +1/4 vs. SR (necromancy spells only)
- Piercing Metamagic Rod: -5 to target's SR
- Dweomer's Essence: +5 vs. SR
- Orange Prism Ioun Stone: +1 vs. SR
- Robe of the Archmagi: +2 vs. SR (arcane casters only)
- Robe of the Resplendent Thespian: +2 vs. SR (bards only)
- Pipes of Dissolution: +2 vs. SR (requires Perform skill)
- Piercing Metamagic: -5 to target's SR
- Spell Penetration: +2 vs. SR
- Greater Spell Penetration: +2 vs. SR
- Allied Spellcaster: +2 vs. SR (teamwork)
- Elven Spirit: +2 vs. SR (half-elves only)
- Demon Hunter: +2 vs. SR (demon targets only)
- Varisian Tattoo: +1 vs. SR (for a single school)
- Bloodmage Initiate: +1 vs. SR (for a single school)
- Spell Specialization: +2 vs. SR (single spell only)
- Sure Casting: +5 vs. SR for next spell cast
- Strength of the Land: +1 vs. SR (dwarf only)
- Earthbound: +2 vs. SR (dwarf only, and air subtype targets only)
- Dedicated Defender: +1 vs. SR (when adjacent to dying ally)
- Precocious Spellcaster: +1 vs. SR (single 1st-level spell only)
- Inquisitor, Piercing Judgement: +1 + (CL/3) vs. SR
- Bard, Sandman Archtype: +2 vs. SR (target must be denied Dex)
- Sorcerer, Seeker Archetype: +4 vs. SR (bloodline bonus spells only)
- Druid, Menhir Savant Archtype: +1 vs. SR for one round
- Lantern Bearer, Numinous Potency: +level vs. SR
- Divine Scion, Opposition Alignment: +1 vs. SR (opposite aligned targets)
In addition to all of the mechanical methods to gain bonuses against SR, there is an additional very simple tactic...use spells that do not allow SR in the first place. A number of conjuration spells allow direct damage, without allowing SR (things like Acid Splash or Acid Arrow, for instance). There are also some debuff spells that don't allow SR, such as Glitterdust. And of course, buff spells generally aren't subject to SR either.