Plants of the World Online : 27 posts by 7 authors.
POWO now contains all Vascular plant families and is now 97.8% complete for species names. 
Worth trying by entering a search. Appears to be better than the Plant List. 

Thanks ...  This is really a wonderful resource for taxonomists..
great. this is then the avatar Kew has been talking about. site says its initial focus is on tropical Africa
However, a mere compilation only. Accepted names and synonyms need not be taken for granted.
Some improvements such as images and references can be noticed.
I did not find it of much use to me. If distribution is any state in India, I think it shows whole of India in the map. 

its saying its started with tropical africa only. it may take them a while to fine tune all regions. as of now its tropical africa nly

NO images in the site ??

Sometimes I find a few illustrations. 

I am not able to see the diversity of the family, i.e. how many genera and how many species? Is it available in the site?

I think although numbers are not provided, one can see the genera under a family and species under a genus, by searching on it. 

this site gives you the whole thing at your fingertips. i think i am going to love it and so will new people and old people who can look up the salient points to photograph i think, i may be wrong but thats what i think just yet.
1: go to the site by clicking on the link ... gave you get a one line query area
2: type family, enter by pressing the magnifying lens, you get a screen with some random species but on the right upper side there is a white window with a button that says Family and hax a X next to it
3: press that x as if trying to get rid of it. next screen you get is all families  starting with Acanthaceae, there are 560 results in 24 pages
4: move your cursor to acanthaceae. a blue frame develops around it
5: move your arrow /cursor to acanthaceae and press left click once on your mouse
6: next screen comes up with descriptions,  images, accepted genera, synonyms. other data etc. i got 201accepted genera for this. scroll down to find some more data.
I punched on Hypoestes. got description. some salient features photos. distribution in world. accepted species. i randomly picked hypoestes lanata. and got to see the four herbarium specimen pictures they have in their database.
i went back to acanthaceae. picked justicia. then j adhatoda and got to see the painting commissioned by  william Roxburgh and several herbarium digitized and some references. 
see if you like it. can be fun and informative. tell me how you did with my steps.
ps remember this is just related to african flora yet

Thank you ...  Much improved than its precursors but the nomenclature issue is based on literature only.

Very interesting! did you try my steps?

Yes. This website is far better than the others, keeping aside IPNI which is the replacement of Index Kewensis.

i am glad for your positive feedback

Yes ... I have tried and reached to same conclusion. The number of genera (given as accepted genera) is available on the page of family but total number of species in a family is the problem. One has to total all accepted species in all genera of a family to reach this number which is difficult in larger families. The Plant List was more convenient for such data and I am accustomed to it. Familiarity with POWO will take a little time.
One more thing- now they have images with names; the power of images for identification is realized.
point well taken. the plant list is still active. the new site is just africa related. not world wide. so has its limitations but i liked access to old pairings and herbaria. in addition to some examples of photographs-
i dont think the plant list site disappear. we could peruse both. cant we?
Now I am using too.

But not many images for comparing.
but id is not just comparing images. its the taxonomic keys. dissection of flowers, leaves, veins, habit etc
and its a new site, give them time. 8 years ago if someone expected our forum to be everything it is now, could we have met  their needs for photos? and we are still evolving
I shall leave this for expert. However, sometimes helpful to अनाडि like me.

ha ha. count me in your अनाडि dal