I first started looking at Harry Potter forums in the wait for OOTP... then discovered fanfiction on them, (mugglenet), realized there were other sites out there that weren't so crappy, and here I am. I like to read HP fanfiction, particularly if it has good plot and action. I'm always on the lookout for more good fics. My absolute favorites are:

(if you havn't read them you should)

Harry Potter and The Third Key by SlowFox

- This is a post GoF and therefore AU story. It is very unique and not exactly canon... Harry has some very different powers that I've never seen written about, but is not super-powerful. The story also has an excellent plot, and requires patience for awhile until the action starts. Despite the fact that this isn't relaly a dark-harry story this is probably one of the darkest fics I've ever read due to many character deaths and the amazingly large and well written amount of violence. This fic is a definite must for anyone who enjoys action at all.

Only place I know of to find it is in the Files section of the Hero Trilogy Yahoo!Group.

A Stranger In An Unholy Land (the Stranger Trilogy) by Jono

- Its post-OOTP, Harry is transported to another world where he was in league with Voldemort the summer before 6th year. This could be the best fic I've read, it has tight plot, superb writing and amazing action scenes, a must read. It also has two promised, but not yet started, sequels.

- and also at

http://www.fanfiction.net/s/1962685/1/

Sword, Soul, and Defiance of the Hero by Joe6991

- Three separate fics. They're amazing, especialy the battle scenes. Pretty much the only good stories where Harry has a ton of power. Can be found at the authors Yahoo!Group and on schnoogle.

Barb's Serpent Trilogy

- Seen by many as the greatest Harry Potter fan fic(s) (especially the first one), I got to the 3rd chapter when I first tried reading them and stopped. When they were highly recomended to me I tried again and loved them. A must read... although the action scenes aren't really that great.

Barb's author page is:

Harry Potter and the Power of Time by Rosswrock

-Great 6th year story. Great ideas. The original independent Harry story. If only he would update.

and also at http://www.fanfiction.net/s/1657629/1/

A Second Chance At Life and Changes In a Time of War (the sequel), by Miranda Flairgold

- Great action scenes, tons of new an imaginative ideas, vampires, bloodmagic, violence. Post 6th year, probably the best post HBP fics being written.

http://www.fanfiction.net/u/100447/

The Phoenix and The Serpent by Sanction

- This is a lesser known fic but still excellent. It starts off a bit slow, and can be a little fluffly at times, but its all worth it for the some the amazing dueling scenes. The author treats the war more as a conventional conflict, with territory being taken and direct attacks being made. Also, because its post GoF, some of the authors ideas are a bit different from what people might be used to in an HP fic, which makes it interesting.

and also at

http://www.fanfiction.net/s/637123/1/