Of course, this question is completely dependent on your own abilities. But I have found that painting - if you have the time - is something you can do yourself. If you're exceptionally handy, tackle electricity. I find plumbing to be more challenging. And since heating and air conditioning, usually require someone who knows how to install an AC or furnace, that tends to be better left to those that do it regularly.
But in these days of economizing, you may be tempted to try refinishing hardwood floors or drywalling yourself. I'm pretty handy, but I'll tell you, I think these two jobs are better left to the professionals. It's not that you can't do it or figure it out, but the smallest mistake can look HUGE when the work is done. And undoing and refixing your mistakes will cost more.
Given the tight times and lack of home building going on, you should be able to negotiate a good price on work. Get three bids. If two bids are similar, negotiate them. If they're all over the place, take the one in the middle and try to get another bid in the same general price area. Then negotiate between the two.
In all cases, good luck!