I've been using RescueTime for two weeks now and am really enjoying it. I have two feature requests that I believe would double the value for anybody who uses MS Outlook.
1) Intergration to Outlook to record scheduled meetings (appointments of type Meeting or Recurring Meeting).
2) More granular recording of Outlook time (I spend about 30% of my time in Outlook it would be really valuable to understand what is spent on Tasks vs Mail etc).

Have you thought about integration with Twittermap? This is hardly a high priority, but the implementation is likely dirt simple. Looking at their API, it appears that a single HTTP call is all it would take, provided you have the location data already available in a format they can parse.

I'd love to be able to search though commit history either based on keywords. I spend a good amount of time figuring out what other team members did, and being able to search for concepts throughout the history of commits would be killer for me.

I don't know if you would want to have search terms applied to commit mesages, code content, or usernames, but there is definitely a chance for some interesting features here. Perhaps, instead of search, take advantage of tagging...that would work quite well with the Lighthouse integration.

This is no small task, but you could probably add some of this functionality just by tossing acts_as_ferret onto changeset models. (BTW, I'm assuming this is built in Rails and not .Net...I know Wildbit does both) This could definitely grind your server pretty hard, though.

I want to use mail and its todo lists with checkoff. I've found mail's todo lists very unwieldy (I don't want to use my mail program to do checklists, and the checklist system isn't as clean or organizable with folders and colors...), but I think if you add the ease of checkoff to it all, things might work out rather well. I don't know a ton of cocoa programming or a lot about mail, but if you'd like to see something done about seeing if integrating mail's todo lists with ical and checkoff, I'd like to see if I could pull it off. All you'd do is say "Send to mail" or "send to ical", and then let those programs do the other dirty work... you'd send it to mail if you want to share a todo list. You'd send a list to ical if you wanted to attach a date to it. I mean, why program that stuff if someone else has already done it? And then, you'd just need to code some way for those to refer back to checkoff, so that as you finish todo lists in any of those apps, checkoff updates correctly as does anything else that refers to the todo lists. Sound cool? It doesn't sound hard, and I've seen people do crazy stuff like that. Let me know if you think it'd be worth looking into this... I dunno how possible it is, but it sounds like people already have apps creating ical events and mails... how much further do you need to go? and on top of that, it'd be really cool if I worked quicksilver into checkoff too.. but I best not get ahead of myself.

Another point of integration with Basecamp would be to integrate with Basecamp milestones.

You could say that a commit completes a milestone, or say that a new tag/branch in the SVN completes a milestone.

This milestone would then be counted as completed in Basecamp.

There is built in integration with Lighthouse for bugs/issues, could the same integration be considered for Google Code bugs/issues?

I would happily go with Lighthouse, except they don't have public projects allowed for free accounts.

I'd love to put that 'this commit fixes bug #111', and have it automatically close that bug in the Google Code issues section.