By my unscientific survey, most DMs think spell components are a neat idea in theory, but a pain in the ass in execution. Players like them less. They get house ruled ("spell component packs"), hand-waved, or ignored all together.
For a time in high school I ran a campaign using the Best of Dragon IV Article, "It's a material world: Scrounging up spell components", which gave guidelines on the cost, source and availability of spell components. We were using AD&D second edition, so we didn't have to worry about swallowing live goldfish or keeping crickets alive, but it still made from an experience full of resource-tracking chaos. It was part of the fun, but we spent a lot of time shopping and searching, time in-session that me and my current players don't have in our adult lives.
My current methodology is to old worry about spell components unless they are expensive (more than 10GP) or particularly rare or cumbersome (black dragon's blood, canine statues). The key one for us has been the 100gp value pearl for identify. The necessity of the Identify spells has created an interesting economy, where players inquire if gems found are pearls, whether moneychanges have any 100gp pearls, and the use of the pearls as a shared party resource.
I've wondered how to create that similar economy and interest for the players for other spells, without the issue becoming a shopping headache. Conceivably we could use small red gems of fire spells instead of bat guano (rubies being inappropriately expensive for fireball), but I fear creating a logical system that overrides the beautiful Vancian incongruency. I do something simular for my ritual system to handle the economics and search procedure, but the form of the component remains to be determined.
Next up for me is a random chart of items, cross-referenced by spell level and school. It will contain a selection of items that seem plausible for regular play - a live cricket would be interesting for a rare ritual, but nothing a character could reasonably expect to use "in the field".
What should be on the list?
