Following this strategy here I post the direct link to the books from the "Faune de France" collection (http://www.faunedefrance.org/BibliothequeVirtuelleNumerique).

Take a look. I hope that can be helpful, at least for European researchers/students.

here some really useful sites for algae:

http://www.algaebase.org/

http://www.szn.it/SZNWeb/showpage/124?_languageId_=2

and some books in italian:

http://www.minambiente.it/sites/default/files/archivio/biblioteca/protezione_natura/dpn_fitoplancton_volume1.pdf

http://www.minambiente.it/sites/default/files/archivio/biblioteca/protezione_natura/dpn_zooplancton_volume2_testo.pdf

http://www.minambiente.it/sites/default/files/archivio/biblioteca/protezione_natura/dpn_zooplancton_volume2_tavole.pdf

Thanks Bachisio!

Regarding to Microalgae, the ACOI website (collection of microAlgae at the Department of Life Sciences, University of COImbra, Portugal, one of the largest of Europe in number of culture strains) can be considered quite interesting and useful. You can find some guides (in Portuguese) and a large image gallery of microalgae identified up to the species level. The website is in English.

http://acoi.ci.uc.pt/index.php

Beetles of Europe (in German)

http://www.coleo-net.de/coleo/html/start.htm

Beetles of Poland (in Polish, English). Strictly speaking not an ID key but numerous photos of most of the species occurring in Central and Northern Europe

http://coleoptera.ksib.pl/?l=en

I'd recommend http://www.efloras.org which contains keys from Floras for a number of countries.

A system that simplifies keys and has been in development and in use for many years are the lucid keys: a number are here: http://www.lucidcentral.com/

Also there is the scratchpad system which is meant for the taxonomic community and other experts to place in one location species descriptions, keys, floristic lists, and even references to DNA data: main site: http://scratchpads.eu/

example: http://cyperaceae.e-monocot.org

As for bivalves I really don't have much to offer but your question seems general despite your specific interests.

May be www.eol.org is one such website

In general, crowd sourcing approaches through citizen science portals like iNaturalist.org are extremely helpful. You can batch upload, geotag, and flag if you need help with ID. The online community typically gets anything unknown resolved rather quickly or at least puts you in the right Genus. But you need a photo of the organism - very critical. Full disclosure, I am a curator there of a project on sea turtles, check it out here inaturalist.org/projects/hawaii-sea-turtle-monitoring

Dear All,

I think many can use successfully the following home pages

http://www.faunaeur.org/

http://data.gbif.org/species

for contacting an expert, getting relevant information on scientific and common names as well as on species distribution and other taxonomic helpful data.

We are beginning to add available literature keys and links to other online guides to the WoRMS database as an 'identification resource' see herehttp://www.marinespecies.org/deepsea/keys_guides.php. This is a new initiative but we have completed it for many of the deep-sea amphipods, tanaids and pycnogonid family levels so far.

Tammy

If you are looking into a broader perspective look into EOL and Bold Datasystems. The last has a complement of genetics associated with photos and morphological characters. However a lot of projects are private.

If you are looking into marine life Worms is the best because the main experts are taking care of it and the synonyms of the valid species. Then you have the specific ones like Fishbase, Algaebase and World Porifera Database.

All are usual tools initially but do not consider them the main source of scientific information because a lot of errors are there. Moreover a lot of data is incomplete as well.

https://marineplankton.net