How can I align tick labels so the tick label text ends centered under the data point? Of Course it works fine with a rotation of 90 Degrees, but not with 45 or similar angles.
I see an example of how to do this charts but not with Plot or ListPlot https://mathematica.stackexchange.com/a/2656/388
d = Table[n, {n, 10}]; xticks = Table[{n, Rotate["The y value is " <> ToString[n], 45 Degree]}, {n, d}]; ListPlot[d, Frame -> True, FrameTicks -> {{Automatic, None}, {xticks, None}}] 
Similar to Szabolcs's and my answers here, I would suggest writing your own custom tick function, so that the labels are set into a Pane which can be both Rotated and have ImageMargins.
myTickList[min_, max_, seg_, shift_?NumericQ, phi_?NumericQ, len_: 0.01] := Table[{i, Rotate[Pane[Style["y =" <> ToString[i], LineSpacing -> {0, 12}], FrameMargins -> {{shift, 0}, {0, 0}}], phi], {len, 0}}, {i, If[Head[seg] === List, Union[{min, max}, seg], Range[min, max, seg]]}] Examples:
fakedata = Accumulate@RandomVariate[NormalDistribution[0, 0.5], 40]; ListLinePlot[fakedata, Frame -> True, GridLines -> {None, Automatic}, FrameTicks -> {{Automatic, Automatic}, {myTickList[0, 40, 4, 25, Pi/4], None}}] 
ListLinePlot[fakedata, Frame -> True, GridLines -> {None, Automatic}, FrameTicks -> {{Automatic, Automatic}, {myTickList[0, 40, 4, 5, Pi/3], None}}] 
Brett Champion posted a nice clean method in Labeling a bar chart, changing how rotated labels are centered that can be applied here as well:
center = Row[{#, Invisible[#]}, "\[NegativeThickSpace]"] &; d = Range[10]; xticks = Table[{n, center @ Rotate["The y value is " <> ToString[n], 45 Degree]}, {n, d}]; ListPlot[d, Frame -> True, FrameTicks -> {{Automatic, None}, {xticks, None}}] 
FromCharacterCode[Table[62340, {x}]] and play with the value of x until it looks good. x=4 was the magic number for me. $\endgroup$
xticks = Table[{n, Rotate["The y value is " <> ToString[n], 45 Degree], {0, 0.2}}, {n, d}];and you'll see that it intersects the text at its midpoint $\endgroup$