Bouldering venues that stay dry during rain...
Lakes
Red Wall
Bowderstone
Wales
Carreg Hylldrem - dry in torrential rain.
Parisella's - can suffer from humidity
Roadside
Drive By wall (40m right of Pill Box Wall on Marine Drive) - Can be dry when the cave is minging. http://www.northwalesbouldering.com/newsitem.asp?nsid=602
Yorkshire
West Vale - bits stay dry in showery weather.
Woodhouse Scar - Clingen Face
Almscliff - Virgin
Ilkley - Calf (Westerly wind)
Brimham - Joker's Wall
Baildon - Right hand side is possible in light rain, especially if there is a northerly wind.
Northumberland
Heckley - bone dry in torrential rain
Back Bowden - some limited stuff under the big roof.
Peak Lime
All steep lime venues stay dry in the rain once dry, but can seep after rain. some of these are Conie’s Dale, Dog’s Dinner, Nuda’s Tartan, Blackwell Dale, Squirrel Buttress, Raven Tor, Rubicon, Dirtlow(!), Anston Stones, Pleasley Vale.
Venues that don't seep, but can suffer condensation are:
Andronicus Cave
Stoney - Minus Ten
Odin Cave - Dry in torrential rain, but can be wet on humid days.
Peak Grit
Churnet - Wright's and Genlteman's
Burbage - Westside story stays dry in moderate rain if weather coming in from the west
Burbage - Leotard Legend
Stanage - Green Room slap is pretty shower proof, thanks to enclosed nature.
Turningstone Edge - Stays dry in moderate westerly rain. Not very many problems though.
Eastwood - Steep rock, capping roofs and woodland keep the bouldering dry in all but the worst conditions.
Shining cliff - The Goose Creature buttress is protected from rain by capping roof.
Cratcliffe - Hueco and Babu Yagu wall are dry in most weather
New Mills Tor
Gardoms - Problem under Spanish Fly roof at Gardoms
Filthy Crag Q - whilst not rainproof it’s super quick drying and sheltered from light showers due to tree cover.
Hobson moor - back wall traverse and problems there on, stays dry in rain as long as its not seeping
Lancs
Brownstones - Nexus Wall. Only a small wall, but lots of minus ten style eliminate dynos. You have to stay close to keep dry though.
Wilton - Horrobix overhang, eliminate potential and problems up to 7A.
Longridge - Can stay dry in rain, but seeps afterward.
Egerton - Problems under the bridge stay dry in rain, but can seep.
Daan South
Huntsham - Rainy Day Buttress. Bouldering (a tad crumbly). And a BIG roof that goes at E8 6c if you fancy it. Guidebook says its one of the largest free ceilings in the country.