http://starbruin.com/ashitanojoe.html
http://www.4shared.com/dir/2439531/705aed58/sharing.html
I love this series. It's about a street deliquient, Joe Yabuki, who comes upon an old drunken man one day and pics a fight with him. Joe kicks the crap out of him, and danpei (the old man) was a boxing trainer and realises that Joe has potential to be an awesome boxing star. Well, He confronts Joe and he's not interested at all. Though, eventually he follows him around and Joe starts learning boxing basics and stuff.
Well then, Joe is sent to jail for corruption (he's invovled in some scandels) and Danpei sends him letters teaching him how to box.
Well Joe bascially ignores the letters and inventually tries to escape from jail, but Toru Rikishi (an ex boxer) stops him and knocks him out with 1 punch. Determined to get Rikishi back he follows Danpei's instructions on the letters. Eventually because of the letters Joe starts to like boxing. He ends up boxing with Rikishi in Prison with Danpei as his trainer, and it results in a doube KO from Joe's Cross counter. After that, Joe is even more determined to get back at rikishi and after Rikishi is released from prison and they vow to settle it in the pro ring.
That's a very basic description so to say. The first couple volumes are kind of slow, but once the boxing tournament happens in the prison, it gets very addictive. It's a great series, but only 5 volumes are scanlated, but there are updates about every week or 2.
It has 20 volumes in general, and the last page of the manga is simply amazing.
btw links at the top are for scans.
Definietly give this series a try. It's awesome. You'll really like it if you like boxing.