I use the Firefox extension Slogger for posting links and bookmarks to del.icio.us, via Spurl: it's the fastest and most effective method I've found. Slogger is set to log pages when the toolbar button is pressed (I'd locally log all visited pages in the background too, but the 'prompt for details' option is linked for both manual and automatic logging - apparently this could get fixed soon); this pops up a panel for adding Tags and a Description. As the page is being submitted to Spurl, the Clip field is filled in automatically when text is selected on the page - this Format script (Options > Services > Spurl > Format..., just a small modification to the default) copies the Clip field to the Description field in quotes, so that when Spurl automatically forwards the post on to del.icio.us the description field will contain the quoted snippet:
var URL = varDetail.URI;
var title = varDetail.title;
var keywords = varDetail.keywords;
var description;
var clip = varDetail.clip;
var desc;
if (clip){ desc = '"' + clip + '"'; }
else{ var desc = varDetail.desc; }
var separator = sloggerPrefs.getPref("spurl.separator");
var priv = sloggerPrefs.getPref("spurl.private");
var explicit = false;
var part = varDetail.linkURI;
part = this.joinSubmissionStrs(part, separator, varDetail.imageURI);
part = this.joinSubmissionStrs(part, separator, desc);
description = part;
var descriptionSaved = description;
var descriptionTemplate = sloggerPrefs.getPref("spurl.descriptionTemplate");
if (descriptionTemplate != "") {
description = this.getStrFromTemplate(descriptionTemplate, varDetail, false, false, false);
}
var cancel = false;
This way I get a searchable fulltext archive in Spurl, more usable link storage and sharing in del.icio.us (plus another way of searching the fulltext of stored pages using Cocoalicious), as well as a local archive of each page that Spotlight can pick up.