<SELECT MULTIPLE SIZE=5>
<OPTION VALUE="o1">Option 1
<OPTION VALUE="o2" selected>Option 2
<OPTION VALUE="o3" selected>Option 3
<OPTION VALUE="o4">Option 4
<OPTION VALUE="o5">Option 5
<OPTION VALUE="o6">Option 6
</SELECT>

Gives:

Option 1 Option 2 Option 3 Option 4 Option 5 Option 6

Or:

<INPUT NAME="options" TYPE="CHECKBOX" VALUE="o1">Option 1<BR>
<INPUT NAME="options" TYPE="CHECKBOX" VALUE="o2">Option 2<BR>
<INPUT NAME="options" TYPE="CHECKBOX" VALUE="o3">Option 3<BR>
<INPUT NAME="options" TYPE="CHECKBOX" VALUE="o4" CHECKED>Option 4<BR>
<INPUT NAME="options" TYPE="CHECKBOX" VALUE="o5">Option 5<BR>
<INPUT NAME="options" TYPE="CHECKBOX" VALUE="o6">Option 6<BR>

Gives:

Option 1
Option 2
Option 3
Option 4
Option 5
Option 6

---

References
http://www.siteexperts.com/tips/html/ts16/page1.asp