i mostly use these free reverb plugins
glaceverb is good for what it does, a giant luscious reverb.
epicverb is good if you need something more versatile.
kjaerhus classic reverb does more convincing small room verbs, and can be useful for fattening things up. btw, all of the kjaerhus classic plugs have a similar character to them. works for some stuff, but not everything.
oldskoolverb kind of does what it says. i don't use this much, but it doesn't sound like the others and gets used here and there.
and these delays
analogic delay, bionic delay, echolive for analog type delays. these things can make some really trippy sounds. love em. they're all of the same type sound and function, but have different features, analogic being the simplest.
watkat is a tape type delay. it's not versatile, but definitely fun for what it does.
valhalafreqecho is a fun toy to play with. move the shift knob, and go from there. you'll see.
mountainecho does a slappy echo. i don't use this one much, but good to keep around for occasional use.
all of the above mentioned plugins, would be considered character type plugins rather than clean/transparent stuff. if i had to pick one reverb and one delay from all of the free plugins that i've tried, i'd have to go with
epicverb and analogic (maybe this will help you widdle down your choices).
is there a free and transparent reverb kicking around out there somewhere?