Here is an online copy of the Index Astartes articles as
GW used to print them in White Dwarf years ago. Quite an interesting collection of Marine fluff, going deep into things like Chapter history as well. Maybe this helps with the research, too.
jareddm wrote:http://wh40k.lexicanum.com/wiki/Main_Page
The go to place for easy to access 40k lore. Though always make sure to check the sources cited, as on occasion something gets lost in translation.
I think the bigger problem is that this wiki attempts to merge sources that simply may not have been intended to tie into each other in the first place. Readers can easily walk away with an individual editor's personal interpretation believing it to be some sort of "truth", rather than forming their own.
My own advice would be to not only check the sources cited, but actually prefer them to the article itself, basically using Lexicanum like some sort of index. Although some articles are indeed 1:1 copies of their respective source rather than a mix; I'd wish that was more common.