Everyone is in a different place financially. We have a mortgage as our only debt and refinanced the mortgage (4.125%; 15 year fixed) early this summer. We have 10.4 months worth of essential living expenses in our mid-term savings and we contribute the maximum allowed to our Roth IRAs (long-term savings) and our short-term savings is on target for our plans. In May 2009, we had a major flood and, as a result, ended up renovating most of the downstairs (combo DIY and professional -- all with insurance payout).
Therefore, if we happened upon $30K, we'd do the following:
~ Our goal is to pay off our mortgage by the time our DD goes off to college in about ten years, so we'd put about $7K towards the mortgage now and that would put us loosely on target.
~ Another goal is to have one year's worth of essential living expenses in our mid-term savings by year-end, so we'd calculate what it would take to make that happen now (less than $3K).
~ The last few things we need to replace in our home (we purchased a fixer-upper ten years ago) include: bathtub/shower in hall bathroom; shower in master bathroom; cabinets in kitchen; windows (we already replaced the sliding doors last summer); and furnace. We already have a financial plan for the windows and furnace (just about fully funded), but haven't done the research required on where and what exactly to buy. The bathrooms are arranged in such a way that replacing the bathing facilities would necessitate redoing the whole room (each). If we were to replace the kitchen cabinets, we would need to replace the sink and counters, as well. Frankly, we would take the opportunity to change the entire layout of the kitchen at that point. We haven't gotten very far in either of these areas, so I don't know what it would cost or what we really want. We typically do a combination of DIY and professional services (taking into account skills required, expenses, and timelines), so costs could really vary.
Ultimately, the remaining money from $30K ($20K+) would go into our house, but we'd park the money in our "high-interest" ( 
at how relative that term is) online savings account until we did the research and were ready to move forward.
OR ---> Maybe we'd find a good deal on a different house and combine the $30K with the proceeds from the sale of our current house, which would net us about $190K (appraisal value from April minus current loan balance), and be able to keep our monthly mortgage where we want it while getting more space in the common areas in order to be able to entertain more than a handful of guests at a time. Plus, we'd want a garage to house our vehicles and a slightly larger yard (ours is minuscule at this time). We haven't found what we are looking for in our current school zone, which we love, so we're biding our time and loving where we are. Once DD gets to middle school, we'd be ready to explore other opportunities since our high school is less than stellar. So, really, that would mean parking the $30K somewhere for 2+ years (she just started 4th grade). The only necessary improvements on our house for resale would be the furnace and we already will be replacing it soon without any of the hypothetical money.
OR ---> Perhaps we would decide to use half of it sensibly (plan A above - first two items and put $5K towards third bullet point....specifically furnace/windows/hall bathroom) and then spend the other half on passports and travel for the next few years! That'd be soooo much fun!!!
I'd divvy up the $15K and use it for at least three ten-day vacations (one a year starting in 2011) and put each chunk into a different savings vehicle with a little more risk for the second and third chunks (for a little higher potential returns). This is actually my favorite plan of all and I bet DH & DD would go for it.
Perhaps a new violin and a bow. Or a trip. But it would only be a small bit of the $30,000.
