Shadow Dancer Requirements:
Skills: Move Silently 8 ranks, Hide 10 ranks, Perform (dance) 5 ranks.
Feats: Combat Reflexes, Dodge, Mobility.

Class Skills The shadowdancer’s class skills (and the key ability for each skill) are Balance (Dex), Bluff (Cha), Decipher Script (Int), Diplomacy (Cha), Disguise (Cha), Escape Artist (Dex), Hide (Dex), Jump (Str), Listen (Wis), Move Silently (Dex), Perform (Cha), Profession (Wis), Search (Int), Sleight of Hand (Dex), Spot (Wis), Tumble (Dex), and Use Rope (Dex).  Skill Points at Each Level 6 + Int modifier.

HD: 1d8
BAB: Per cleric (3/4)
Strong Saves: Reflex
Weak Saves: Fort, Will

Level 1: Hide in Plain Sight

Level 2: Darkvision, Evasion, Uncanny Dodge

Level 3: Shadow Illusion, Summon Shadow

Level 4: Shadow Jump 40' max distance, 4 Jumps per day

Level 5: Defensive Roll, Improved Uncanny Dodge, 5 Jumps per day

Level 6: Shadow Jump 60' max distance, 6 Jumps per day

Level 7: Slippery Mind, 7 Jumps per day

Level 8: Shadow Jump 80' max distance, 8 Jumps per day

Level 9: 9 Jumps per day

Level 10: Improved Evasion, Shadow Jump 100' max distance, 10 Jumps per day

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Evasion (Ex) At 2nd level and higher, a shadowdancer can avoid even magical and unusual attacks with great agility. If she makes a successful Reflex saving throw against an attack that normally deals half damage on a successful save, she instead takes no damage. Evasion can be used only if the shadowdancer is wearing light armor or no armor. A helpless shadowdancer does not gain the benefit of evasion.  If a character gains evasion from a second class, the character automatically gains improved evasion (see below).

Summon Shadow (Su) At 3rd level, a shadowdancer can summon her own shadow. While active, the shadowdancer casts no shadow.  Though it has the stats of an undead shadow, it is actually an extension of the shadowdancer's spirit. The summoned shadow cannot be turned, rebuked, or commanded by any third party. This shadow serves as a companion to the shadowdancer.  Initially, the shadow may only communicate via emotions, though it can instintively sense what the shadowdancer wants it to do.  The summoned shadow advances based on the shadowdancer's character level as given below.

If a shadow companion is destroyed, the shadowdancer must attempt a DC 15 Fortitude save. If the saving throw fails, the shadowdancer loses 50 experience points per character level. A successful saving throw reduces the loss by half, to 25 XP per prestige character level. The shadowdancer’s XP total can never go below 0 as the result of a shadow’s dismissal or destruction. A destroyed or dismissed shadow companion cannot be replaced for 30 days.  During this time, the shadowdancer casts no shadow.

Shadowdancer Familiar advancement:

Char                    Bonus            Nat Armor               Dex

Level                    HD                      Adj                         Adj                      Int               Special

1st-12th               +2                        +1                          +1                       6                   Empathic Link

13th-15th             +4                       +3                           +2                        7                 Improve Speed +10ft

16th-18th             +6                        +5                          +3                       8                  Share Spells/Share Save

19th-20th            +8                         +7                          +4                       9                  Imp. Evasion/Telepathic Link

Shadow Jump (Su) At 4th level, a shadowdancer gains the ability to travel between shadows as if by means of a dimension door spell. The limitation is that the magical transport must begin and end in an area with at least some shadow.   A shadowdancer can initially jump 40' per jump, and can jump a number of times per day equal to her class level.  At level 6, her distance per jump increases to 60'.  At level 8, it increases to 80'.  At level 10, she may move 100' in a jump.  This is a move action that only triggers an attack of opportuinity if the shadowdancer leaves a threatened square.  Skills or feats that prevent attacks of opportunity also apply to this type of movement.

Otherwise per SRD.  I'll let Oni post what we came up with for the Mirrorshard PrC.

My only problem with it: Why should they get it as a move action when the spell 'dimension door' is a standard action? Are we trying to allow them to have an attack after?

Yes we are.  This was a point that Oni and I discussed to some length, and we both felt that since shadow jump was one of two definitive class abilities, it should be a move action only.  Notice that the ability is supernatural (Su) vs. spell-like (Sp).  Without the ability to act in combat after a jump (a single attack), the movement is almost worthless, as it puts the SD at the mercy of their foe.