Good thread Chris.
Others to catch around now: photos not to hand.
- on Lesser Celandine. There are 3-4 rusts, but one forms smallish spots visible on the top of the leaves, and a characteristic rust coloured spot on the underside (Uromyces dactylidis).
- Sweet Violet. a couple of rusts, but the one I've seen recently on leaves and petioles was Puccinia violae.
- Oregon Grape. Mahonia rust Cumminsella mirabilissima. Look for leaves discoloured a darkish burgundy colour. Turn them over and the underside of the leaf will have a rusty felted appearance.
- Meadowsweet: a bit early yet, but this is a spectacular (and under-recorded) rust. Probably occurs everywhere Meadowsweet grows.
All of these are gall causers as well.