What is it?
Rebar simply provides text values for your the health and mana of your character, your pet (if you have one), and any party members next to their respective status bars (in the default Blizzard UI) rather than on top of them. It also provides the same values for your target and focus frames, and for the game tooltip, although in this case the values are on top of the corresponding bar.
For each frame type (player, pet, target, focus, party, or tooltip) you can individually control whether text is shown, and whether it is shown as deficit (how much is missing) or percentage value. For the target, focus, and tooltip frames, Rebar also recognizes friendly units (those that you can assist or cast heals on) and non-friendly units, so as to allow you to chose different settings for these.
Why write this?
In the 2.3 client, Blizzard added the option to show values or percentages on the player, pet, party, and target bars. However for me, the text of these values just gets in the way of being able to easily see where my status bar is at, and doesn't provide individual control for health and mana. It also doesn't provide a "deficit" mode to show how much health or mana is missing (something that I find very useful for healing).
How to use Rebar
Rebar remembers all of the settings you make in the options window on a per-character basis (since what is useful for your healer might not be so helpful for your DPSer). To display the Rebar Options window, just type /rebar or /reb.
Rebar has a number of settings that are global configurations, and don't have to be configured per character - font sizes per frame (set via the /rebar size command) and whether text should be shown all centered or not.
The CT team for CT_UnitFrames which I relied on for so long, and which I missed enough when they weren't around to write Rebar.
Reparent RebarTooltipFrame to GameTooltipStatusBar to ensure it gets hidden when it is supposed to (stops it showing a value on tooltips it isn't supposed to).
Minor fix to help text highlighting
Changed version string to 3.2.0
Added code to handle vehicle frames for the player and party so that their text values appear in the right place.
Added code for displaying the health (as a value, deficit, or percentage) on the mouseover-tooltip.
Added the option to set the sizes of the text on the different frames through the size command.
Added the option to display text on the player, party, and pet frames centered instead of to the side.
Added an entry for Blizzard's interface options screen that shows a list of the slash commands, tidied up the help text, removed the normal addon "announce".
Various code legibility improvements (particularly for the way defaults were handled).
Honour the lockColor option for statusbars in HealthBar_OnValueChanged.
Set justification of the font to match that of the frames to improve on-screen alignment.
Raise the level of the Rebar text so that it shows up properly above the artwork for its unit frame.
Hide frames that aren't being used because the user has turned off its options.
Changed version string to 3.1.0
Fix issue that arises when logging in on a newly created character or after reinstalling WoW due to client messages arriving in unexpected order.
Changed version string to v3.0.2.
Fixed a bug where the health status bars weren't being colored according to the health value.
Added new options for friendly versus non-friendly health settings for your target and focus-target.
Made the tooltip descriptions in the options a little clearer.
Changed version string to 3.0.1
Changed version string to v3.0.0.
Added support for the new Blizzard default FocusFrame
Added support for the new "fast updates" mode for player and pet mana
Tweaks and improvements to the options menu
Change to support the new method where PC and NPC health is always reported
Status option now shows memory used
Various minor changes for version 3.0 compatibility