I don't know of any sites you can use but in my opinion you would be best of buying some books like 'Kanji in Context' and just learning to read by... well... reading.
Also you can use the firefox plugin 'Rikaichan' to read websites.
(But if you do this, don't allow Rikaichan to become a crutch)
I say this because I get the impression you are trying to learn each reading for each kanji seperatly (Based on the type of site your asking for)
But when you come across words like 長年 and 長時間, how will you know how to read 長? for example.
Anyway, it is only my opinion, but I think the majority just learn to read, by reading.
Rikaichan:
rikaichan | polarcloud.com
Kanji in Context:
Kanji in Context Reference Book: Amazon.co.uk: Nishiguchi et al: Books
Kanji in Context Workbook vol 1: Bk. 1: Amazon.co.uk: Nishiguchi et a: Books
Kanji in Context Workbook vol 2: Bk. 2 Kanji in Context Series: Amazon.co.uk: Nishiguchi, Kono: Books
Edit:
I forgot to mention, Kanji in Context has no English in it.
I started using it with a basic knoweledge of grammar and basic knoweledge of 100 kanji (Just to take a wild guess at a number there lol)
It was difficult to start out with, and I asked lots of questions on various forums, but after about 10 pages things got easier.