Long story.... short version is DH finally got paid for work he did a couple years ago. Due to extenuating circumstances, we weren't expecting him to ever get paid for this work. Well, the guy suddenly showed up and paid us in cash. 
Yes, I asked a teller at a grocery store bank to verify some of the cash was real. I also deposited some into our credit union account. All is well on the authenticity front.
We need to use about half for a new furnace and ductwork. Neighbors have paid $2-3K and are happy with their decisions (installers and furnaces/ductwork/warranty/etc.). I need to call the companies and evaluate for myself. My dad is willing to help us do the install ourselves (and we'd help him install a new one in his place, as well). That would lower the cost below my estimate, but we may "splurge" and just pay someone to do the whole thing since we have the cash. Plus, we just did extensive repairs/upgrades ourselves over the spring/summer from a major flood. It is a catch-22 for me. I find I am happier with the quality of work (labor) when we do it ourselves, but it tends to take longer to get the job completely done. We usually opt for a higher quality product and free labor (ourselves), but we do contract out certain aspects of some projects. Our place was built in the 70s and certain things are best left to experts with appropriate equipment and expertise (potential asbestos, unusual mortar/tile removal, super high ceiling, etc). The furnace itself doesn't qualify for professional installers, in my opinion, but the ductwork might (fiberglass, I'm pretty sure).
Our only debt is our mortgage. DH's salary was cut back in January 2009. I called every company we pay and reduced our services to get our bills lowered. We're doing okay, but gave up eating out for the most part this year (for frugal reasons AND health reasons). We used some of the cash to get some restaurant gift cards (roughly $200 in GC for ~$65) for a treat in the new year and it turns out we'll be having a houseguest for a week soon. We haven't decided what to do with the rest.....
For fun (as in a fun discussion), what would you do with $5,000 cash you were not expecting, but earned back in 2007?
Yes, I asked a teller at a grocery store bank to verify some of the cash was real. I also deposited some into our credit union account. All is well on the authenticity front.

We need to use about half for a new furnace and ductwork. Neighbors have paid $2-3K and are happy with their decisions (installers and furnaces/ductwork/warranty/etc.). I need to call the companies and evaluate for myself. My dad is willing to help us do the install ourselves (and we'd help him install a new one in his place, as well). That would lower the cost below my estimate, but we may "splurge" and just pay someone to do the whole thing since we have the cash. Plus, we just did extensive repairs/upgrades ourselves over the spring/summer from a major flood. It is a catch-22 for me. I find I am happier with the quality of work (labor) when we do it ourselves, but it tends to take longer to get the job completely done. We usually opt for a higher quality product and free labor (ourselves), but we do contract out certain aspects of some projects. Our place was built in the 70s and certain things are best left to experts with appropriate equipment and expertise (potential asbestos, unusual mortar/tile removal, super high ceiling, etc). The furnace itself doesn't qualify for professional installers, in my opinion, but the ductwork might (fiberglass, I'm pretty sure).
Our only debt is our mortgage. DH's salary was cut back in January 2009. I called every company we pay and reduced our services to get our bills lowered. We're doing okay, but gave up eating out for the most part this year (for frugal reasons AND health reasons). We used some of the cash to get some restaurant gift cards (roughly $200 in GC for ~$65) for a treat in the new year and it turns out we'll be having a houseguest for a week soon. We haven't decided what to do with the rest.....
For fun (as in a fun discussion), what would you do with $5,000 cash you were not expecting, but earned back in 2007?










and some medical bills.
)

Your words about the quality of labor are so familiar to me. We hardly ever hire anything out. When we do, it's just a disappointment - either in the quality or cost of labor. And sometimes it doesn't even take less time than it would take us to do it, though I know that's likely true in the case of a furnace and I can see the potential for the specialized skill.
)
We've only lived here since September and can't afford to move again.