I have a <textarea>. I want one button that will insert text into it whereever the text cursor is at.

Also one that will insert text at the end of it.

I've been fooling around with it and looking at tutorials, but I can't seem to get it.

I've been fooling around with it and looking at tutorials, but I can't seem to get it

No it can be a real PITA to get working cross browser.

here's something I wrote earlier (I use it on my CMS system) complete with a bonus function to Prepend text as well as Insert (at cursor) and Append.

function insertText(p_oObj, p_sText) {
if (document.selection) {
p_oObj.focus();
var l_sSel = document.selection.createRange();
l_sSel.text = p_sText;
}
else if (p_oObj.selectionStart || p_oObj.selectionStart == '0') {
var l_iStartPos = p_oObj.selectionStart;
var l_iEndPos = p_oObj.selectionEnd;
p_oObj.value = p_oObj.value.substring(0, l_iStartPos)+ p_sText+ p_oObj.value.substring(l_iEndPos, p_oObj.value.length);
} else {
p_oObj.value += p_sText;
}
}

function appendText(p_oObj, p_sText) {
p_oObj.value += p_sText;
}

function prependText(p_oObj, p_sText) {
p_oObj.value =  p_sText + p_oObj.value;
}

demo buttons;

<button onclick="insertText(document.getElementById('textarea'),' Some text to insert ')">Insert some text</button>

<button onclick="appendText(document.getElementById('textarea'),'  Some text to end ')">Append some text</button>

<button onclick="prependText(document.getElementById('textarea'),' Some text to front ')">Prepend some text</button>

Demo assumes the textarea has an ID of "textarea"