1st Division Vice Captain - Chojiro Sasakibe

Not much is known about this man, other than his outfit, which is somewhat different and more formal than those of the other vice-captains. Judging from his appearance, face, and weapon, it is probably a safe guess that he is a sophisticated sort of man.

2nd Division Vice Captain - Omaeda Marechiyo

Descended from one of the noble families in Soul Society. Omaeda is an enormous individual, dwarfing his petite Captain. He is also her opposite in personality, being rather a buffon and not especially bright. Not much else is known about.

3rd Division Vice Captain - Kira Izuru

A thin and somewhat neurotic individual, Kira is good friends with fellow vice-captains Hinamori and Abarai. He seems a decent enough sort, but is also extremely loyal to his captain, Ichimaru Gin. This sometimes puts him in difficult positions, where he is forced to choose between loyalty to his captain and loyalty to his friends.

4th Division Vice Captain - Kotetsu Isane

As kind-hearted and mild as one would expect from the Fourth Division, but seemingly having a slightly more combative nature. She is extremely loyal to her captain, whom she idolizes, and has a sister (Kiyone) who is ranked as third seat of the Thirteenth Division. Not much else is known about her.

5th Division Vice Captain - Hinamori Momo

A sweet, gentle, and somewhat naive girl who seems entirely unsuited to be a vice-captain in the rough and dangerous world of Soul Society. Despite her cute and innocent appearance and demenour, however, she can cross swords with the best of them, and is an accomplished master of kidou.
She has idolized Aizen Sousuke since before she became his vice-captain, and holds an almost unhealthy degree of loyalty to him, particularly in times of extreme emotion.
Hinamori's best friend, however, is Hitsugaya Toushirou, captain of the Tenth Division (whom she calls "Shiro-chan" for short, much to Hitsugaya's annoyance). They have known each other since before they were shinigami, and she seems to love him as though he were her younger brother.

6th Division Vice Captain - Abarai Renji

The personification of "attitude." Renji is almost the exact opposite of his captain, cocky, easily riled, and unsophisticated in his approach. He does not outwardly seem to have much respect for Byakuya, but in reality Renji greatly respects and fears him. It is his dream to one day surpass his captain, and he trains toward this end with almost fanatical fervour.
Renji is friends with Kira and Rukia, with whom he attended the shinigami academy. He bears particular affection--and possibly something a bit more--for Rukia, and he is pained to see her sentenced to death. Though he initially goes along with the orders of Soul Society, Renji grows increasingly resistant as time passes to a course of action he sees as morally reprehensible.

7th Division Vice Captain - Tetsuzaemon Iba

A former member of the Eleventh Division, plainly evidenced by his continued love of fighting. Tetsuzaemon is the very image of a yakuza, with garish tattoos and a tanto (dagger) zanpaku-to secreted in his kimono. He still maintains good ties with the Eleventh Division, particularly with his old friend Madarame Ikkaku, though it is implied that Tetsuzaemon left the Eleventh in order to advance himself more quickly (which naturally caused some bad feelings with his former Division). Tetsuzaemon is a talented combatant and a master drinker.

8th Division Vice Captain - Ise Nanao

A careful analysis of Nanao-chan (as Shunsui calls her) will reveal that she shares much in common with her captain, such as intelligence, compassion, and sensitivity. What distinguishes them, however, is that Nanao is disciplined and businesslike, in stark contrast to Shunsui's often-lazy attitude. As such, she is the discipline and perhaps even the brains of the Eighth Division, working tirelessly to keep afairs in order and patiently enduring Shunsui's endless flirting and drinking. Nanao has a classic strict librarian's personality, complete with glasses and enormous tome.
Despite her common annoyance with her captain, Nanao actually has quite a good relationship with her superior, and the two truly seem to care for each other. She also does not seem to be averse to the occasional social event herself, though one would imagine that she partakes of parties in strict moderation.

9th Division Vice Captain - Hisagi Shuuhei

Brave and talented, if a bit rough around the edges. Shuuhei was a top-level student at the shinigami academy, being offered a ranked spot in the Gotei 13 before he even graduated. His courage was emphasized when a training raid he led as an upperclassman (including Renji, Rukia, and Kira, interestingly) went sour and Shuuhei ordered the rest of the trainees to flee while he attempted to hold several powerful Hollows off.

10th Division Vice Captain - Matsumoto Rangiku

Though most folks probably know her best by her ample... *assets,* Matsumoto is actually quite a capable and loyal vice-captain (if a bit on the lazy side). She has a good relationship with her captain, who--despite his seeming annoyance at her sleeping on the couch during working hours--holds great respect and even admiration for her.
Matsumoto also has the unique (and perhaps dubious) honour of calling Ichimaru Gin a friend. As far as can be determined, she is Gin's only friend, having met long ago while she was training her spiritual energy. She seems to like Gin quite a bit (perhaps in an unrequited manner), and is the only person whom Gin seems unwilling to interfere with.

11th Division Vice Captain - Kusajishi Yachiru

Cotton candy to her captain's tiger, Yachiru seems distinctly out-of-place in the battle-loving Eleventh Division. She is consistently sweet and cute, somewhat airheaded, and totally devoted to her captain (as well as the only person in the world who can get away with calling him "Ken-chan").
Yachiru's perpetually happy personality is well-established; in her infancy, as a nameless orphan, she was quite bubbly and cheerful even among a pile of corpses, where Zaraki found her and named her. Since then, she has accompanied him wherever he goes, gleefully misleading him with her rather bad sense of direction and generally adding a splash of colour to Zaraki's otherwise dark life.

12th Division Vice Captain - Kurotsuchi Nemu

Kurotsuchi Mayuri's "daughter," created by the Twelfth Division Captain to be his loyal servant. Despite being constantly mistreated by her "father," Nemu remains totally obedient, loyal, and devoted to his goals. She is not, however, a fool, or someone to be taken lightly.

13th Division Vice Captain - Shiba Kaien (deceased)

The deceased vice-captain of the Thirteenth Division. He bears a strong resemblance to Kurosaki Ichigo, and was apparently a good friend of Rukia's.