If you're ok with using the mouse, you can use the secondary selection. Press Meta, then click and drag the left mouse button (
M-drag-mouse-1). This doesn't move the point as long as you're only copying text that's visible on the screen. You can copy the secondary selection with
M-mouse-3 and yank it with
Apart from the secondary selection, you will need to move the cursor to select arbitrary text, because the cursor is one end of the selection (the other one is the mark).
If you want to work in a buffer without affecting the point, you can open the buffer in a second window (
C-x 2 or
C-x 3). Each window has its own point. When you've finished selecting and otherwise editing, close the window (
C-x 0) and go back to the other one.
For more flexibility, you can clone the current buffer. Run
M-x clone-indirect-buffer, or
C-x 4 c to also create a new window showing that buffer. The clone has the same text as the original, but it has its own mark and point.
If you've already killed some text, you can append more text by typing
append-next-kill) and then using a kill command. For example,
C-M-w C-k appends the tail of the current line to the text that's already at the front of the kill ring, and deletes the copied text.
C-M-w M-w appends the selection to the text at the front of the kill ring (as opposed to
M-w which pushes the selected text as a new entry on the kill ring).