Some weeks ago, I came across this little wonder called GNU Terminator (or "GNOME" Terminator). It is an unfortunate coincidence that there is another similar tool with the same name (Terminator). I am not going to judge which one is "better". I just use the one at tenshu.net, which is the one that Arch Linux ships as package "terminator".
Terminator is a terminal emulator that allows for splitting of the window into several smaller terminals. Its main advantage over just using tabs (which Terminator can also do), is that all windows are simultaneously visible (main obvious drawback: they are smaller). Its main advantage over opening multiple terminals and tiling them is that (except if a tiling window manager is used, which would also have this advantage) is that Terminator automaticaly avoids overlaps, while maximizing the space usage. Some tools, such as the Grid module of Compiz Fusion can arrange windows similarly. Actually, I have been using this module extensively, and I still do. However, Terminator is more convenient, both because it allows arbitrary sizes (Grid allows windows to occupy an integer number of virtual screen sections, in an imaginary 3x3 grid), and because resizing a sub-terminal automatically adapts all the others, avoiding overlapping and wasting space.
I uploaded a short video to YouTube, showing a basic usage of Terminator. Below the video you can read some explanations of what you see:
We start by opening a Terminator window, and maximizing it. Next, we split the window into 4 terminals. We first split the original terminal vertically, with Ctrl-Shift-o (with a "horizontal" line), then we split each terminal horizontally with Ctrl-Shift-e (with a vertical line). We can act on each terminal individually. To navigate the terminals with the keyboard: Alt-Left for left, etc.
We continue by resizing the terminals. The borders separating the terminals are actually grab bars, so we can drag them with the mouse to move those boundaries, so the terminals resize accordingly. With the keyboard: Ctrl-Shift-Left grows the current terminal (the one with the cursor) to the left, etc.
Apart from tiled terminals, we have access to tabs. To open one, right-click with mouse and select "Open Tab" in the context menu, or with the keyboard: Ctrl-Shift-t. Move from tab to tab with Shift-Left and Right.
Finally, we close the terminals we don't need anymore, and the remaining ones adapt, to always maximize the space used. Closing all terminals will, of course, close Terminator.