I've noticed this on some blogs. When a widget (recent posts, categories, archives, etc.) gets too long and you have to scroll down seemingly like forever, that widget either gets its own page or gets trimmed in some way. I'm here to offer an alternative, but it's not for the code queasy. You'll have to edit your theme by hand.

Let's take my own "Recent Posts" widget (from either the Tiga or Tigapedia themes) and make a scrollbox, changing the one on top to look like the one on the bottom:

Recent Posts Normal Display

Recent Posts With Scrollbox

Step 1:

Find the code in the style sheet that affects the "Recent Posts" widget". In my style sheet, it's called "left-widget":

.left-widget {
border-color:<?php tiga_widgetBorderColor(LEFT);;
width:<?php tiga_leftWidgetWidth(); ?>px;
border-width:0px 1px 1px 1px;
border-style: solid;
color:#000000;
background-color:#f8fbfd;
padding:5px;
margin-bottom:5px;
font-size:13px;
}

Step 2:

Add a new widget to the bottom of the style sheet:

.scrollbox {
border:0px;
margin:-5px;
padding:5px;
width:<?php tiga_leftWidgetWidth(); ?>px;
height:350px;
overflow:auto;
}

a. The border is set to 0 to prevent an extra or double-thick border within the widget.
b. The margin is set to -5px to counteract the 5px from the left-widget.
c. The padding is set to 5px to make everything line up with with widgets above or below.
d. You can specify any height you wish, but it shouldn't be very short. Other items not specified are inherited from the left-widget.

Step 3:

Find the code in your theme that displays the "Recent Posts" widget. Mine is in the "sidebar.php" file:

<!– Begin - Recent Posts –>
<div class="left-widget-title"><?php _te('Recent Posts'); ?></div>
<div class="left-widget">
<ul><?php get_archives('postbypost',tiga_recentPostsCnt(),'custom','<li>','</li>'); ?></ul>
</div>
<!– End - Recent Posts –>

Step 4:

a. Above the line starting with <"ul">, insert "<div class="scrollbox">".
b. After the line starting with <"ul">, insert "</div>

That's all there is to it!

I only did this temporarily to my theme because none of my widgets are that long yet, except maybe the link categories. The cool thing about this is that I can have as many "Recent Posts" as I want and it won't make the widget any bigger.

Eventually, my archive months and my categories will start getting longer than I like. When it gets out of hand, I'll be using this code.