You will obtain the Citdael: Wounded Batarian side quest in the Presidium Commons area by overhearing a human and a turian by the apartments discussing the wounded soldier. Apparently, he was shot during the Cerberus attack on the Citadel and is now being cured. However, these people suspect (along with several others) that the wounded batarian may actually be a terrorist. Head down to the batarian camp in the Docks: Holding Area level, and speak with his nurse. She will let you through to visit him. Talk to him, and he will basically flat out tell you that he is, in fact, a terrorist. At this point, you can either stop his life support, or simply call the nurse back in to complete this mission.
You will find the Target Jamming Technology side quest in the Commons, near C-Sec. A turian officer will be talking about improving the Citadel’s ability to counter targeting systems. You will find the item you need for this quest in the upcoming Rannoch: Admiral Koris quest. During this quest, be on the lookout for a computer terminal that contains the Jamming Tower Data. Return this data to the turian to complete the quest. Alternately, you can simply buy what you need from the Spectre terminal later.
You will get the Hades Nexus: Obelisk of Karza side quest from a human sitting on the benches in the Commons. Head to the Hoplos system and scan the planet Kopis to find the Obelisk that he seeks. Return it to the human to obtain a 15,000 credit reward.
Finally, you can get the Athena Nebula: Hesperia-Period Statue side quest from an asari in the Presidium Commons, sitting on the L-shaped couch on a balcony. She will need the statue to help with work on the Crucible. Head to the Vernio system, part of the Athena Nebula, and scan the planet Polissa to find the Statue. Return it to the asari and you will again receive 15,000 credits.