For information Malpighiales families see the APG website: http://www.mobot.org/mobot/research/apweb/
Useful links for many of the families:
Neotropikey: http://www.kew.org/science/tropamerica/neotropikey.htm
Neotropical Plants Image Database: http://www.kew.org/science/tropamerica/imagedatabase/index.html
Plantsystematics webpage: http://www.plantsystematics.org/
Smithsonian image database: http://biogeodb.stri.si.edu/herbarium/
A. Popovkin: http://www.flickr.com/photos/plants_of_russian_in_brazil/sets/7215759455...
IPM images, University of Georgia, U.S.: http://www.ipmimages.org/about/
Flora of China: http://hua.huh.harvard.edu/china/
Families belonging to the Malpighiales, and additional useful links:
Achariaceae
Balanopaceae
Bonnetiaceae
Calophyllaceae
Caryocaraceae
Centroplacaceae
Chrysobalanaceae
Clusiaceae
Ctenolophonaceae
Dichapetalaceae
Elatinaceae
Erythroxylaceae
Euphorbiaceae s.l.
- Neotropics
Euphorbia Planetary Biodiversity Inventory project (PBI; key, database): http://www.euphorbiaceae.org/
Federal Noxious weed Disseminules of the U.S., Euphorbia: http://keys.lucidcentral.org/keys/v3/FNWE2/key/Other-Key.htm
University of Hawaii Botany Department http://www.botany.hawaii.edu/Faculty/Carr/euphorbi.htm
Euphorbiaceae photos on Flickr:◦M. Huft: http://www.flickr.com/photos/mhuftphotos/sets/72157625100047941/with/557...
- Asia
Euphorbiaceae of Malesia: http://www.nationaalherbarium.nl/euphorbs/
Euphorbiaceae of Thailand: http://www.nationaalherbarium.nl/thaieuph/
Euphroniaceae
Goupiaceae
Humiriaceae
Hypericaceae
Irvingiaceae
Ixonanthaceae
Lacistemataceae
Linaceae
Lophopyxidaceae
(Malesherbiaceae incl in Passifloraceae)
Malpighiaceae
http://herbarium.lsa.umich.edu/malpigh/index.html
(Medusagynaceae incl in Ochnaceae)
Ochnaceae
Pandaceae
Passifloraceae
Peraceae
Phyllanthaceae
Picrodendraceae
Podostemaceae
Putranjivaceae
(Quiinaceae incl in Ochnaceae)
Rafflesiaceae
Rhizophoraceae
Salicaceae
(Samydaceae incl in Salicaceae)
http://tolweb.org/Samydaceae/68361
Trigoniaceae
(Turneraceae incl in Passifloraceae)
Violaceae