This post is not about a particular world, but I often see people on various forums and such asking about some killer software app or website where they can learn, and memorize, kanji characters.
In my opinion, no such site or app exists, because the best, or only, way to learn kanji properly is to write each character out physically many, many, many times.
Before you scoff at the old fashioned concept of putting pencil to paper. let me explain. Kanji characters depend a lot on the stroke direction of each swash or line. (For that matter, some katakana characters do also: can you tell the difference between ソ and ン?) Stroke order is not as important for reading comprehension, but can make a difference when you are writing kanji by hand. And I don't really know of a better way to learn these things than by writing out the characters repeatedly until you develop a muscle memory for how the characters should be written. You can't do that by typing.
If you live in an area near a Japanese bookstore, go and look for a 漢字練習帳 (かんじれんしゅうちょう kanji renshuuchou) - a kanji practice notebook. These have pages with large grids that are perfect for practicing your kanji by hand. They're used by kids in elementary school in Japan. Of course you can always practice on any old piece of paper, but the notebooks are nice to write in.
You can use an online resource to organize your kanji study, but for practice and memorization? Do it by hand.
More than 1000 kanji required to read a newspaper
This page on Wikipedia Japan has listings by grades 1 through 6 of the kanji characters that are taught. The list has changed over time, but basically it's a total of more than 1000 characters (1016 for that list). To read a newspaper, you should know all of these characters. Even for manga you should know most of these characters. Here is another list, which also includes the kanji taught in junior high (grades 7 through 9 in US terms), organized by the number of strokes per character. I don't know how to write out a lot of these off the top of my head, but I can read them.
I haven't written a lot of Japanese (or any other language for that matter) out by hand recently, unless I'm writing an address on an envelope or something. I do most of my writing online, where I can easily look up kanji if needed. I am positive that's lead to a deterioration in internal kanji database. I know I'm not alone in this, because I often see Japanese people writing some very strange kanji online.
So, if you want to learn properly, write it out!
How I learned
In case you are thinking, "She's Japanese, how can she understand how it is for a non-Japanese to learn kanji", let me tell you how to learned all the kanji required to be learned by the 5th grade in a few months, when I was about 10!
I was born in the Tokyo area, and lived there until age 5, when my parents moved to London. I was already reading by that age (see my English Twitter page for a photo of me reading intently at around age 3 or 4...though I'm not sure if I was actually comprehending anything!), but of course mostly kana-base pictured books and such.
For the next 4 years, I attended regular schools in England and didn't learn much Japanese. Then we moved to the U.S., in the summer when I was age 10. My parents knew we'd be returning to Japan the next year, so they wanted to put me in the Saturday Japanese school.
My mother sat me down with a simple book, and told me to read. To her horror, she discovered that I could barely read at all. So, she had a correspondence course for overseas Japanese kids sent over - for grades 1 through 4. From June to September, she sat me down every day, making me go through the correspondence course. The kanji was especially difficult - she made me practice those characters, over and over and over again.
I really hated this...it was summer, and I wanted to be playing with my new friends! I remember threatening to jump out of the window of our 5th floor apartment several times. But my mother perservered. By the time September rolled around, the Japanese Saturday school was not sure that I could keep up with the other 4th grade level kids, but I could, just barely. (I hated going to that school anyway for other reasons, but that's another story.)
The next year, we did indeed return to Japan. Once again the regular elementary school near our new home wasn't sure that I was ready to jump into the 2nd term 5th grade, but they put me in anyway. I remember feeling very strange and foreign for the first few weeks, but after that I really had little problem. I could keep up fine with all the lessons. And that summer of intensive drilling by my mother was what brought me up to speed, despite all the grief I gave her. (One of these days I'll remember to thank my mom for that.)
So you see, I'm living proof so to speak that pencil-on-paper drilling really works! It's hard and boring, but really sticks.
*This post was inspired by this question on Ask Metafilter, where there are suggestions for online learning resources. I haven't tried any of them myself but maybe you'll find one there to suit you.