I've been trying to make the Top News/Everything tabs in the Latest Activity module stand out a bit more - for the benefit of members.

There may be more simple code to use but here is what I'm using (added to Appearance - Advanced)

.activity-feed-view-selector {
border-bottom-color: black;
}

.xg_module_body ul.activity-feed-view-selector li {
display:inline-block!important;
display: -moz-inline-box; /* inline-block for earlier versions of FF */
-moz-box-orient: vertical; /* inline-block for earlier versions of FF */
display: inline-block;
vertical-align: middle;
*display: inline; /* ie7+ hack */
*vertical-align: auto; /* ie7+ hack */
padding-right:0.5em;
padding-left:0.5em;
}

.selected-activity-view {
font-size: 18pt;
border-style: solid;
border-width:1px;
border-bottom-color:#74ade1!important;
border-bottom-width:2px;
margin-bottom: -1px!important;
}

.activity-feed-view-selector li.activity-feed-view-options-links-delimiter {
color:#74ade1;
}

And you can see the effect on The Mod Generation

ps where I've used the color #74ade1 this is simply to match the background color of the module and make these elements disappear - so you should change for your own background color