Due to fan demand, Wizards of the Coast has posted a rough and dirty conversion guide to convert your 3.5 characters to 4th edition. It may not be quite as detailed as people like, but I think its pretty good given the radical differences between the two systems. I really like the Monk conversion guidelines.

Monk
At a glance, the player with a 3E monk might think that he’s out of luck until the 4E monk releases—there’s no unarmored, unarmed melee fighter option anywhere in the Player’s Handbook. However, with your DM’s permission you can create a martial-arts striker who captures much of the monk’s style by following this process:

Choose the two-blade ranger build (p104). (Don’t worry, this will make sense in a minute.)

Give up your leather and hide armor proficiencies, gaining a +3 bonus to AC when wearing no armor or cloth armor. You’re now only a point behind the normal ranger’s AC.

Gain a +2 bonus to Will defense (in addition to the ranger’s normal defense bonuses).

Replace Dungeoneering and Nature on your class skill list with Arcana, Diplomacy, Insight, and Religion. Choose five trained skills from your class list.

Give up your martial weapon proficiencies. Grant your unarmed strike a +3 proficiency bonus, increase the damage to 1d8, and add the off-hand property. Now you’re wielding two melee weapons that are as good as the martial melee options available to the ranger.

Rename Hunter’s Quarry as Monastic Battle Focus, and lose the Prime Shot class feature. (You thought you were getting that +2 bonus to Will for free, didn’t you?)

Focus on mobility-oriented powers, particularly those that reward a high Wisdom score (such as evasive strike, yield ground, and weave through the fray). As desired, you can rename those powers with a flavor that befits your monkish heritage (peerless balance of the crane instead of fox’s cunning, for example).

Pick up feats to recreate other 3E monk class features—Evasion, Fleet-Footed, Long Jumper—and use multiclass feats (p209) to replicate the supernatural features. For example, the warlock has several teleportation powers reminiscent of abundant step.
This doesn’t faithfully recreate every element of the 3E monk, but it’s definitely a reasonable stopgap if you’re really committed to sticking with the character. Feel free to experiment with additional tweaks, and by all means please share your results on the D&D message boards!