Just recently got back into Pokemon, and while I don't have a lot of specific things to trade, I can provide a couple of services for people who ask.

I am capable of transferring Pokemon from Generation III to V, and own the following games:
Ruby (have access to it)
XD: Gale of Darkness
Black2 (Have access to it)

This means that I can offer the following:

Purified Shadow Pokemon
Just completed my first playthrough, and plan to eventually do another. Most species are still available for trade, but the following are not:

Generation III Move Tutors
From XD, Colosseum(Maybe) or LeafGreen. XD has all of the moves available, including Mimic currently. Leafgreen has most of them to my knowledge, aside from Softboiled and Mimic.

Services aside, these are Pokemon that I can trade:
Latias (HG, Lv.35, UT, Brave)
Ho-Oh (HG, UT, Quirky)
Mewtwo (GenIII and GenIV, did not yet encounter)
Articuno (Shiny, UT, Mild, Lv50)
Rattata (Shiny, UT, Hasty, Lv3)
Liepard (Shiny, +ATK,+SPD, Naughty, Lv20)
Dusknoir (Shiny, Bold, Lv43, Mimic Glitch was used on it. I can remove the illegal moves upon request)
Victini (Lv15, UT, Bashful)
Electrode (Lv3, UT, Hasty)
Keldeo (Lv15, UT, Calm)
Pikachu (50, Hasty, +SPD, +SPA, Mimic Glitch'd for Surf)
Moltres, Zapdos (Gen III and IV, no encounter yet)
Lugia (XD001, nature not yet revealed)
Ralts (Lv20, UT, Careful, has Sing from XD)
Snorunt (Lv20, UT, Gentle, has Sing from XD)
Scizor (Lv40, UT, Naughty, has Morning Sun, Swarm)
Banette (Modest, Lv37, UT, Cursed Body/Cotton Guard from Dream World)

These are the Pokemon that I am currently seeking:
Technician Scizor with Morning Sun - I wish it happened on my playthrough of XD, but sadly, it did not. I doubt anyone else has this, but just in case.
Drought Ninetales (Shiny) - Not counting on this, and might be able to do it on my own eventually, but will still keep an eye out.
Prankster Sableye / Murkrow (male is fine if it has good nature, moves, etc)
Any foreign Ground Egg Group Pokemon (Preferably Darumaka)
Solar Power Char(mander/izard) - with any nature that does not negatively affect SP.ATK
Drought Politoed (or its pre-evolutions)
Shiny event Entei / Raikou
Wish event Pokemon
Magic Guard Abra
Regenerator Slowpoke
Marvel Scale Dratini
Technician Shroomish / Breloom
Speed Boost Torchic / etc.

Generally, I am looking for Pokemon with Hidden Abilities, or non-Uber Legendary Pokemon that are rare or from some sort of event. I'll look at almost anything. I prefer nicknames, and have them for most Pokemon that I put up for trade.

Lastly, I just ask for your patience in dealing with me. I don't frequent this site as much as a normal person does, though I'll try to be consistent.
(Moderators, if there is something wrong with this post, do not hesitate to remove it)