Since the new Kindle DX is so good for reading manga, I'm really interested in manga ebooks now. Does anyone have any good sources?
The ones on Amazon are mostly yaoi and erotica, which is fine, but I'd like to get some shojo and shonen and josei as well.

I just discovered NetComics the other day.
I'm not really sure how they work (if they'd go on the Kindle or what), but they seem to have a variety of titles, though most of them are Korean, going by a superficial browse: http://www.netcomics.com/

manga is generally really fast to read. can you 'turn the pages' fast on a Kindle?

Yes, it's really fast. I don't notice a delay at all.

I know that OverDrive has a few of Tokyopop's manhwa and OEL series available. However, it's a library service, so not only would your library have to subscribe to it, they would also have to purchase those particular series.

my library has quite a few ebooks that you get online, so I would not be surprised if they got some.

What are manga ebooks? Are they the ones that you can find online? If they are than I can give you three great places.
http://www.mangafox.com
http://www.citymanga.com
http://www.mangable.com
You shouldn't try www.onemanga.com or www.1000manga.com because they don't have any more manga on there now.

Mangafox is not a source of manga ebooks. I don't know about the other two sites. OneManga isn't either. Those sites are manga readers, but don't have ebooks available for download. (And if you're on a Kindle, you want to be able to download actual ebooks.)
There's another site that I found very recently, but I can never remember what the address is. It's legit manga ebooks, owned by the folks who own June. DMP, I think?

I don't think I've ever seen or heard of manga/manhwa ebooks. I've seen comic ebooks though. You could possibly download mangas off of a place like mangatraders and turn them into a pdf file if you really wanted to. And from there convert them to whatever the kindle format is.
Although imo that's more hassle than it's worth.

you can download manga/manhwa ebooks. I've seen a few sites. Though I don't like downloading them.
'If you can read it online, don't bother downloading.' -that's what I would say.

10> Not everyone can spend time online while reading - downloading is good for reading while away from an internet connection, for example. Plus, it's easier to access the book if you have it saved to your computer/ereader than if you have to go online every time. Also, loading the images is faster if you have it saved.

It takes up too much space on your computer though..
And besides if yu have a fast internet service then it won't take that long to load.
P.S. Where do yu store the downloaded manga ebooks when yu don't have any internet sevice?

Manga ebooks really don't need to take up that much space. Also, I invested in an external harddrive for backups (which I really need to get around to doing..) - it's 500GB and cost less than $100 (it was a christmas gift, so I don't know exactly how much was paid). I store my ebooks either on my laptop's harddrive, a 2GB USB drive I have, or on an old laptop's harddrive that I converted into an external. I have plenty of space for them (it's the video and music files that suck up all the storage space!).
I delete the ebooks I've downloaded if I don't intend to read them again, or I just redownload them again if I feel like it.
Really, though, saving the scanlated manga or digital manga from official sources to your computer (or e-reader or whatever other device) is the way it's been done for a long time. Online readers didn't really get going until 2007 or 2008, you know.

If you have a livejournal account this http://community.livejournal.com/manga_epub/profile was created a couple of days ago.

In annother topic, someone asked about Chiro Star Project. I found a site that has all the volumes, but you have to download them first. Maybe you can try adding them to your ebook reader.
http://han-file.blogspot.com/2009/06/chiro-star-project.html

I think you can download e-books here..:
http://egscans.com/

I just noticed that Yen Press offers a free app for the ipad in order to read manga ebooks. I dont know if you can read them on other e-readers.